At the mention of the words "erotic," "vulgar," and "naked love god," I brace for Jason's inevitable dirty joke, but all I get is a distracted "uh-huh." He's typing away on his phone, not even looking up.

Jason continues with his nose in his phone, so I find another empty spot at the foot of the fountain and open my guidebook. I can be distracted, too. But as I flip the pages, I find I can't focus on any of the words or pictures. I feel strangely anxious. I haven't seen Mark at all today or heard from him, either. I did get a text from Chris, but it didn't give me the buzz of excitement it has in the past.

All my attention is on Mark, and my attempts to be rational about his sudden appearance in London are not working. Sure, we had a great day yesterday, and he walked me home and let me keep his sweatshirt (and I totally didn't sleep with it, I swear), but that's hardly a declaration of love. Still, I can't seem to shake the blah feeling that's overtaken me.

It doesn't help that Jason is acting stranger than normal. He's barely spoken to me, though he has managed to impersonate me falling into the pond three times today. The only things that seem to be distracting him right now are the living statues scattered around Piccadilly Circus, and that's only because he's taking great pleasure in taunting them. I feel bad for them (really, I know their pain all too well), but I'm also thankful he's teasing someone other than me. With the icky feeling resting on my shoulders, I mostly just want to be left alone.

But as the day wears on, Jason's cold shoulder makes me feel worse and worse. I can't help running through the last few days: the almost kiss on the London Eye, the full-on make-out session in Stratford-upon-Avon, the note in which he called it all a mistake.

And then yesterday's weirdness with Mark. Jason was so hostile. There was definitely something going on, some kind of history between them that even Mark didn't realize, because he acted cool and calm in the face of Jason's insanity. I tried bringing it up once or twice already, but Jason got all cagey and changed the subject. It's downright bizarre. I could ask Mark, but I don't particularly want to bring him into all the ridiculous drama that is my junior class trip. Maybe there isn't a good reason for it. Maybe Jason is just taking pleasure in being an ass, which really wouldn't shock me in the slightest.

I close my book hard, pressing the covers together between my palms. I close my eyes and try to clear my mind of all the craziness that seems to be hopping around like a million little Jasons playing pranks on my psyche.

"Uh, I hate to interrupt your meditation, but I'm headed into Lillywhites." I open my eyes to see Jason towering over me again, his thumb pointed over his shoulder at the famous London sporting goods store. "I want to get a soccer jersey to take back with me."

"Football," I mutter wearily.

"Whatever," he says. "I'll be back in a bit. I'll find you here later?"

"Yeah," I sigh. "Sure." I rub my temples, but it doesn't soothe the dull ache in my skull. I put my head down in my lap and take a few deep, cleansing breaths like my swim coach has us do before a meet. The oxygen floods my lungs and brain, and I actually do feel a little better. When I look up, the scenery isn't so painfully bright anymore, the tourists not so cacophonously loud.

I scan the square and spot Jason. He's stopped outside the entrance to Lillywhites. He's engrossed in that damn phone again, but he quickly snaps it shut. His eyes dart around like he's looking for someone, and then he turns and walks away.

He's ditching me.

I'm suddenly furious. He wouldn't let me ignore him-no, he wore me down by being nice ... all so he could use me as a cover!

What a manipulative little ...

His ball cap bobs across the square and disappears down the steps of the Piccadilly tube station. Without consciously deciding to follow him, I hop up from my spot on the step and hurry after him. I'm sick of being lied to. I'm tired of being used.

And I want to know where in the heck the little weasel is going.

When he gets to the bottom of the stairs, I jog after him. I find a particularly tall businessman with broad shoulders and duck behind his pinstripe suit. When the train arrives and the doors slide open, I hop on the opposite end of Jason's car. I can see his reflection in one of the windows, and I keep my eyes trained on it so I'll know when he gets off.

The train whooshes down the track, and I grab the pole to keep myself from toppling over into the tired-looking woman next to me with the screaming baby in her arms. I make a mental note to find the hand sanitizer in my bag when I get off the train. Each time the train stops, I have to strain to keep Jason in my sight while people rush onto and off the train. First Green Park, then Hyde Park Corner. As we approach Knightsbridge, I see him move toward the doors. This is it. I take a deep breath. The train stops; the doors slide open.

"Mind the gap," the automatic voice trumpets, and people begin rushing off, including Jason. My heart pounds hard as the electronic ding alerts us that the doors will soon close. And right when I think I might burst from waiting, I finally leap off the train as the doors are sliding closed.

Jason moves fast along the platform, weaving through commuters and tourists. He's hoofing it with such purpose and speed that I don't worry about him turning around to catch me following him. He jogs up the stairs to the street and down Brompton Road, and I follow him, leaving a half block between us.

We don't go very far before he reaches his destination. Harrods. Famous like Macy's but expensive like Bendel's. Looming over an entire city block, the ornate building just screams "money." If the Gossip Girls came to London, this is where they'd shop. In fact, I'd be willing to bet all the books in my bedroom that this is where Evie and Sarah have been spending their cultural hours.

Jason disappears through one of the brass-and-glass doors, and I scurry after him. I pause by the door, though, and give myself a quick once-over in one of the spotless store windows. I remember vividly the passage in my guidebook detailing the Harrods dress code. There are stories about the staff denying entrance to all manner of famous people for even attempting to enter in flip-flops, no matter how diamond-studded. I am not about to be thrown out of here looking "unkempt," as the vague language stipulates.

Unfortunately, one look at my reflection, and I realize that "unkempt" seems to be my personal style. I run my fingers through my tangle of curls in a failed attempt to tame the frizz, and press my hands along my shirt. My sweaty palms do have a sort of steamer/iron effect on the wrinkles, and I feel satisfied that I'm probably not going to get booted from the store.

Once inside, I'm assaulted by an oppressively spicy smell. I've entered right into the men's fragrance department, and sexy suited men are all around, offering squirts of the latest designer scent.

"Craving by David Beckham?" a thick, syrupy British voice asks.

"What?"

Apparently, that's the magic word, because a spritz of something ends up right in my face and up my nose and in my eyes and on my tongue. I hack and gag and nearly spit right on the floor of Harrods.

"So sorry, sir," the clerk says. Sir? I stop coughing long enough to give him the nastiest look I can muster, and he hops back in shock. "Oh, dear me. I'm so sorry, ma'am. I, uh, didn't realize."

"Whatever," I mumble, brushing past him. Great. Now I'm dressed like a homeless person and I smell like a gigolo. They're going to have bloodhounds on my trail to get me out of here, and thanks to this stupid cologne, I'm going to be way too easy to find.

I wander away, rubbing my eyes to rid myself of David Beckham's latest celebrity scent. I blink hard a few times to clear up my foggy vision, and I have a brief moment of burning panic when I think I've lost Jason. But I quickly spot his rusty mop bobbing up the escalator. I scurry through the dense crowd of shoppers and hop on, trailing him slowly, mechanically, to the next floor.

I keep my focus trained on Jason's back, noting that when he reaches the top, he makes a quick U-turn off the escalator. Seconds later I emerge into the most glorious displays of designer shoes I've ever seen. Phoebe would be in heaven.

I see a flash of red hair underneath a navy Sox cap; Jason has hopped another escalator. I tuck my shoulders and duck my head as I follow him onto the escalator, positioning myself directly behind a blue-haired old lady in an enormous honey-colored fur coat. She's got a fluffy little yip of a dog tucked under her arm, and the color of the pup's fur is so close to the color of the coat that I worry she's destined to become a matching hat.

Safely hidden behind Cruella de Vil, I am able to follow Jason up three floors, past towers of luggage fit for a jaunt on the Titanic, mountains of fluffy towels I'd never dream of washing my face with, something called the Bed Studio. I immediately imagine Jason using all the beds as a personal trampoline; then, as soon as I have Jason and beds in the same thought, visions of wet grass start to snake into my brain. I lift my right foot and stomp down hard on the left to rid myself of the image.

We finally arrive at the fourth floor, where Jason steps off the escalator and pauses to look around. I have to perform a complicated shimmy-hop off the top of the escalator to avoid crashing into his back, and I duck behind a Juicy Couture-clad mannequin.

I count to ten, then peek out from behind the swaths of candy-colored terry cloth. Jason is on the move again and once again I follow him, ducking low behind dresses and blouses until he hangs a sharp left. I pop up from behind a display of Burberry trenches. He's headed into the Pet Kingdom, an opening flanked by two large porcelain Dalmatians on pedestals. I wait a moment until he's safe inside, then hurry across the crowded hallway to follow him. I'm temporarily distracted by the glass cases filled with dog shoes.

That's when Jason turns around. Maybe he's lost for a moment, or maybe he senses he's being followed. Whatever the reason, he throws a quick glance over his shoulder. Fortunately, I have just enough time to dive behind the counter of the doggie bakery in the corner. I crouch behind the pink-and-white striped counter, trying to block out the smells of liver and bacon by nestling into my David Beckham-sprayed hoodie. When I'm satisfied that Jason hasn't seen me, I slowly peek my head up over the counter and peer through the display of biscuits shaped like signs of the zodiac. I see the back of his head disappear out the opposite end of the Pet Kingdom, and breathe a deep sign of relief.

"Miss? Excuse me?" A perfectly coifed middle-aged woman in a navy suit is looking down at me. "Is there some kind of a problem?"

"Oh no, I'm okay," I reply, sighing. "I just need a moment. You know, to rest."

"Well, I'm going to have to ask you to leave," she says with her clipped British accent. All of a sudden, she sounds exactly like that evil headmistress from A Little Princess, and I feel the same cold terror I felt when I was first introduced to the character when I was five. I look up to meet a gaze so icy I feel like she's shoved me into the Charles River in the middle of January. "We simply don't tolerate this kind of behavior at Harrods."

I mutter a quick apology and bolt for the exit before she can take my arm like some schoolmarm and march me out to the nearest Wal-Mart. I can escort myself out, thankyouverymuch.

Be careful. I wouldn't want to see you get hurt -S Great. I follow Jason halfway across London and then lose him in Doggie Heaven.

I start circling back toward the elevator that leads to the street. I wind my way through maternity, baby, children's, and juniors, an entire luxury life cycle unfolding before my eyes. It seems like I'm nearly back to where I started, and I have yet to find the escalator that brought me here.

By this point, it's a familiar feeling. Ever since that party and Jason and my little texting exploration, I've been trying to get back to the Julia Lichtenstein who boarded the flight in Boston. Heck, I'd give anything just to be Book Licker again. But as soon as I think I've found her again, she's gone, replaced by this crazy girl who leaves a field trip to follow Jason Lippincott.

Up ahead is something simply called the Diner, where I can see that the Brits have decided to approximate a real American diner experience. Red vinyl booths, gleaming white Formica countertops, and shiny chrome as far as the eye can see. Of course, the luxury version of a classic American diner gets one very important thing wrong: it's all too clean, too shiny, too perfect. My favorite diner back home, the Deluxe, features tarnished chrome, chipped counters, and duct-taped stools at the bar.

Still, for a moment, I feel a sharp stab of homesickness. Deluxe was Dad's place, and as soon as I was born, he made it our place. He used to take me there every Sunday morning for breakfast, even when I was an infant. He loved to tell me how he'd put my car seat right on the counter next to his bacon and eggs. It was Mom's morning, he said, for her to sleep. But it was also our morning.

As I grew older-old enough to sit on my own stool, my little legs swinging below the counter, old enough to order my own pancakes-it became less about Mom sleeping in and more about me and Dad.

I spot Jason, his Sox cap resting on a tabletop, his red hair running wild across his forehead. He's sitting across the table from a blond girl, though "blond" isn't enough to describe her shiny, luxurious, perfectly straightened locks. Her flawless skin looks like a team of angels has been standing around spritzing her all day. She's wearing a perfect swipe of ruby-red lipstick. This girl is so classy she can wear what my mother refers to as "hooker lips" at midday and not look a bit like she's charging. A pair of milk shakes sits between them, Jason's half gone and hers nearly untouched.

They lean over the table at each other, talking conspiratorially. She pushes a slip of paper across the table, and Jason gives it a quick read, then shoves it into his pocket. He pulls the straw out of his milk shake and tosses it onto the table, tips the glass back, and finishes it in one long gulp. She laughs and reaches out and touches his hand. For some reason, seeing that-the gentle way she brushes his skin with her fingertips-makes my stomach dive all the way to my toes.

When they stand, I see she's nearly as tall as he is.

She leans in closer to him, and my heart stops....

Are they going to kiss?

Just then a very large Hawaiian-print monstrosity slips in front of my view. A large man in pleat-front khaki shorts and a silk shirt in an abomination of colors points a fat finger toward the diner. "Honey, look! I bet I can get a cheeseburger just like at home!" Of course a guy like that travels thousands of miles to eat the same crap he'd eat at home ... for twenty dollars more a plate. I lower my gaze, and it's what I suspected: he's wearing socks and sandals. I hop left, then right, finally getting a clear shot around Mr. Hawaii, but Jason is already giving the girl's hand a final squeeze and turning to go. Whatever happened, I missed it.

Then, abruptly, he turns in my direction. Now that Hawaii has moved on, I realize I'm standing right out in the open. There's nothing for me to hide behind, so I simply spin around and walk quickly in the opposite direction, my sneakers squeaking on the marble floor as I scurry. I spot a sign for the "Ladies' Lounge," which I assume must be a bathroom, and make my way straight for it.

Inside, I'm greeted by a gleaming entryway, a luxurious gilded sofa against one wall. I sink into it and take some deep breaths, willing myself to stay calm. My brain won't stop firing questions at me, though: Who was she? Is that who Jason's been texting all day? Where did he meet her? Did they kiss? He kissed me. Now he uses me as his alibi so he can go kiss her?

As quickly as the questions come, my brain provides the answers: She's a supermodel. She met Jason at that house party. She was charmed by his American sense of humor and brash behavior. They've been carrying on an elaborate affair via text message. They met up to cement their newfound relationship. He wants her. Bad.

"Ugh," I groan before bending over and placing my forehead on my knees.

"Can I get you anything, miss?" I look up to see a grandmotherly attendant in a Harrods uniform looking concerned.

"No thank you, I just need a moment," I reply. I try to arrange my mouth into some approximation of a smile. What appears must look more pathetic than anything else, because she pats me on the shoulder.

"I understand, dear," she says. "Take as long as you need."

I thank her, then drop my head back into my lap. I wish I could drop to the floor to do some push-ups, but somehow I do not think Harrods tolerates that kind of behavior, either. All my muscles are tight, and that spot between my shoulder blades starts to ache. I take a deep breath, rolling my head to loosen my neck. Quiet, quiet, I repeat to myself, and after a few more deep breaths, I finally feel ready to leave. I thank the attendant on the way out, dropping some coins into the silver bowl by the door, and head back for the escalator. This time, Jason really is nowhere to be found, thank God.

I ride the series of escalators back down to the street, and with each floor, I descend deeper into a foul mood. He was supposed to be helping me; that was our deal. But I don't have Chris, and he's done nothing but sabotage things with Mark. He's been playing me all along, and I have no idea why. He flirts with girls to get room keys and Internet access and also, apparently, just for sport! And he's good at it, which is what really kills me. He's managed to find out enough about me to manipulate me (like playing on my love for the Beatles) so that he can get exactly what he wants, from a kiss to a cover to a pile of reflection papers. He's not helping me; he's helping himself. And now he's helping himself to the most gorgeous girl in Britain. Jason has been carrying on some kind of secret romance? All this time I've been confiding in him, kissing him, and he hasn't even bothered to mention the supermodel he's got in his pocket? I mean, sure, I've been asking for his help with Chris ... and it's not like Jason owes me anything....

I feel like I've swallowed a bunch of live eels. It's true. Jason doesn't owe me anything.

But he made me think that he cared....

My thoughts are ping-ponging so fast it makes me dizzy. I am completely mortified. Why settle for the girl who pretends to be a supermodel when he can have an actual supermodel? It's utterly humiliating, and I feel the shame in my stomach rolling around with my breakfast.

I can't shake the image of her ruby-red lips, and the next thing I know, I'm imagining them kissing. I try to tell myself I don't care if he did-if he does. I want to kiss someone else. Someone like Mark. I try to imagine what it would be like to have Mark's strong arms around me, pulling me close. I try to imagine his lips on mine, but the image keeps disappearing right before I get to the good stuff. Instead, all I can see is an alternating slide show of Jason kissing me, then Jason kissing that girl. And then it all makes sense. That's why kissing me was a mistake. He was probably thinking about her the whole time, and once he came to his senses and realized it was Book Licker in his arms, he bolted.

No wonder Sarah keeps telling me to back off. Thinking back to that awful look of pity she gave me at Buckingham Palace, I realize she wasn't trying to keep Jason for herself. She was trying to protect me from Jason and his lies. She was only warning me away from him! Maybe she's not the super villain I've always thought, but now my whole world seems upside down. Mark is flirting with me, Jason kissed me, and Sarah Finder is being nice to me? Up is down; down is up!

When I'm back on the street, I turn to head toward the tube and the rest of my class. Jason is probably headed there himself, and it won't take him long to realize I'm gone (or will it?). As I make my way down the street, I feel the anger building up inside me, and also the pain of the shock.

I don't know why I'm so surprised by the way Jason has been using me. But I am surprised. Surprised and hurt. For a while, it seemed like he was turning into something else. Someone else. Like maybe he was going to let me see some other side of him. But even that was all a lie. There is no other side. It wasn't a betrayal, really, since we never had anything to begin with. A mistake isn't a relationship.

If I can go back to ignoring him, just like before this trip began, then I can forget. Jason isn't important. Mark is my MTB! Mark never makes me feel so horrible and confused and conflicted. Mark makes me feel good. That's what an MTB is all about.

It doesn't matter. IT. DOESN'T. MATTER. I repeat the words in my head with each step, over and over, until I'm actually whispering them aloud as I march down the street.

I thought I saw u today, outside of Harrods? (not stalking u I promise!) ;) -C Jason is standing in front of Lillywhites. He's got one foot hiked up on the building and I notice his knee poking through a hole in his jeans. (How did he not get kicked out of Harrods for that?) He leans against the brick exterior like he's been there all day, and when I walk up, he lazily looks up from his phone.

"Hey, Book Licker, where ya been?"

"Where have I been?" I say, the anger starting to bubble up, but I quickly slam the lid down tight on that pot. I don't care. I don't care. I repeat the mantra over and over until, instead of exploding, I return a lazy shrug and pull my phone from my bag to click through it. "Oh, you know, just exploring."

"You blowing up?" he asks, nodding at my phone while he flips his own shut and returns it to his pocket. "Met lover boy yet? He get a hold of you?"

"I'm actually hoping to hear from Mark," I say, not taking my eyes off the phone, a sly smile on my face. Can he see that I don't care? "I think we might try to get together tonight, maybe go for a swim or something." Jason jerks back a little bit, as though I've reached out and slapped him. "What happened to Chris?" Jason says. I keep moving, so he's forced to direct the question to my back.

"Well, I don't know Chris. I know Mark," I reply. I don't turn around.

"Do you?" he says, his voice edged with coldness.

At this, I whip around to face him.

"I know he's a totally sweet, totally nice, totally cute guy who doesn't act like a five-year-old or push me into ponds," I say.

"Touche," Jason says, but he doesn't smile. His expression is completely blank. There's a moment of thick silence between us, and I refuse to speak first. I will not speak first. I. WILL. NOT- "What have you been up to?" I ask. Dammit. My curiosity and desire to catch him in a lie trump whatever other game my head wants me to play.

"Oh, you know," he says. He lets out a long breath. "Exploring. Taking in the culture. Readying myself for the excitement yet to come."

"What kind of excitement are you expecting?" I ask. I want to trip him up; I want him to mention Harrods or that girl or the texts he's been getting all damn day. He's too smart, though. Or maybe too good a liar.

He doesn't get to answer. We're interrupted by a stream of our classmates pouring out of Lillywhites, some loaded down with bags. They move en masse toward the fountain, our designated meeting point. Ryan runs between us, a shiny new lacrosse stick in his hand. He's waving it so wildly that I have to duck to keep my front teeth. When I stand back up, Jason is pushing off the wall with his foot.

"Never a dull moment with me, Book Licker," he says.

I trudge through the doors of our hotel behind the rest of the class. Everyone is chatting excitedly about their new purchases. All I can think about is a swim. Or a nap. Maybe a swim and then a nap.

The class rushes for the elevators, so I head straight for the stairs. I want to fall right into my bed, and I don't want to run into anyone between here and there.

I climb the three narrow flights to my floor and throw my body into the heavy metal fire door. It flies open and I stumble through it.

Colliding directly with Mark.

"Hey!" Mark exclaims, reaching his arms out to steady me. My face lands right in his chest, my cheek nuzzling the softest butter-yellow sweater ever.

"Oh my gosh!" I say, breathless from the climb. I step back out of his arms and straighten my hoodie, red creeping into my cheeks. "So sorry!"

"Hey, no problem. Just my luck, actually. I've been looking for you all morning!" he says, that big almost-perfect grin I love so much spreading across his face. "I was hoping we could do some more exploring, maybe grab some lunch. I loved wandering with you the other day."

"Of course!" I burst out. I guess playing hard to get isn't my forte. I can feel the muscles in my neck and shoulders melt like butter the color of his sweater, which goes perfectly with his dark hair and spring tan. While I've been running around looking after Jason, Mark has been looking for me all morning? Finally, someone who's chasing me. Just like that, I'm not tired anymore. "But maybe we could avoid ponds or other bodies of water this time?"

"Of course," he says, grinning. He leans against the wall, his arms crossed over his chest. I swear, he looks like a cologne ad I saw last month in Teen Vogue. "You crack me up, Julia."

Oh my God. He thinks I'm funny. And not in a clumsy-funny or dorky-funny way. I'm filled with the warm, happy sensation of sipping hot chocolate in front of a fire on a snow day.

Mark nods toward the elevator in one of the effortless nonverbal communication moves that only truly cool people are ever able to pull off. I follow him.

"What did you have in mind?" I ask.

"I don't know, let's just walk. How does that sound?" His voice is relaxed, easy.

"Perfect," I reply. My chest feels full, and I let out a long breath. The fullness is still there, though. But this time I know it must be happiness. "Let me run to my room and grab my map."

"No way," he says. He presses the brass down button, and the elevator bursts open like it was waiting for us. He gestures into the elevator. "Let me be your guide." Then, in a tone of deliberate casualness: "You don't need to find Jason or anything, do you?"