'Goodnight,' she says, and ends the call.

Before he goes to bed he puts on Chopin's opus 25, to hear what he's aiming at. When he hears the pianist Maurizio Pollini's bubbling notes, he can't help laughing.

11.

The sun is high above the trees, and the blue-and-white plastic tape is fluttering in the breeze. A transparent shadow of the tape dances on the tarmac.

The police officers posted at the cordon let through a black Lincoln Towncar, and it rolls slowly along Stenhammarsvgen as a reflection of the green gardens runs across the black paint like a forest at night.

Margot Silverman pulls over to the kerb and glides smoothly to a halt behind the command vehicle, and sits there for a while with her hand on the handbrake.

She's thinking about how hard they worked to try to identify Susanna Kern before time ran out, then, once an hour had pa.s.sed and they realised it was too late, carried on anyway.

Margot and Adam had gone down to see their exhausted IT experts, and had just been told that it wasn't possible to trace the video clip when the call came in.

Shortly after two o'clock in the morning the forensics team were at the scene, and the entire area between Bromma kyrkvg and Lillngsgatan had been cordoned off.

Throughout the day the arduous task of examining the crime scene continued as further attempts were made to question the victim's husband, with the help of psychiatrist Erik Maria Bark.

The police have carried out door-to-door inquiries in the neighbourhood, they've checked recordings from nearby traffic-surveillance cameras, and Margot has booked a meeting for herself and Adam to see a forensics expert called Erixon.

She takes a deep breath, picks up her McDonald's bag, and gets out of the car.

Outside the cordon blocking off Stenhammarsvgen is a growing pile of flowers, and there are now three candles burning. A few shocked neighbours have gathered in the parish hall, but most of them have stuck to their plans for the weekend.

They have no suspects.

Susanna's ex-husband was playing football at Kristineberg sports club with their son when the police caught up with him. They already knew that he had an alibi for the time of the murder, but took him to one side to tell him.

Margot has been told that after he was informed, he went back in goal and saved penalty after penalty from the boy.

This morning Margot drew up a plan for the initial stages of the investigation in the absence of any witnesses or forensic results.

Paying particular attention to people convicted of s.e.x crimes who have either been released or given parole recently, they're planning to track down anyone who's been inst.i.tutionalised or attended a clinic for obsessive disorder therapy in the past couple of years, and then work closely with the criminal profiling unit.

Margot crumples the paper bag in her hand while she's still chewing, then hands it to a uniformed officer.

'I'm eating for five,' she says.

Wearily she lifts the crime-scene tape over her head, then walks heavily towards Adam, who is waiting outside the gate.

'Just so you know, there's no serial killer,' she says sullenly.

'So I heard,' he replies, and lets her go through the gate ahead of him.

'Bosses,' she sighs. 'What the h.e.l.l are they thinking? The evening tabloids are going to speculate, it doesn't matter what we say; the police are fair game to them, but we have to follow the rules. It's like shooting a f.u.c.king barrel.'

'Fish in a barrel,' Adam corrects her.

'We don't know what effect the media are likely to have on the perpetrator,' she goes on. 'He might feel exposed and become more cautious, withdraw for a while ... or all the attention could feed his vanity and make him overconfident.'

Bright floodlights are shining through the windows of the house, as if it were a film location or the setting for a fashion shoot.

Erixon the forensics expert opens a can of Coca-Cola and hurries to drink it, as though there were some magic power in the first bubbles. His face is shiny with sweat, his mask is tucked below his chin, and his protective white overalls are straining at the seams to accommodate his huge stomach.

'I'm looking for Erixon,' Margot says.

'Try looking for a ma.s.sive meringue that cries if you so much as mention the numbers 5 and 2,' Erixon replies, holding out his hand.

While Margot and Adam pull on their thin protective overalls, Erixon tells them he's managed to get a print of a rubber-soled boot, size 43, from the outside steps, but all the evidence inside the house has been ruined or contaminated thanks to the efforts of the victim's husband to clean up.

'Everything's taking five times as long,' he says, wiping the sweat from his cheeks with a white handkerchief. 'We can't attempt the usual reconstruction, but I've had a few ideas about the course of events that we can talk through.'

'And the body?'

'We'll take a look at Susanna, but she's been moved, and ... well, you know.'

'Put to bed,' Margot says.

Erixon helps her with the zip of her overalls, as Adam rolls up the sleeves of his.

'We could start a kids' programme about three meringues,' Margot says, placing both hands on her stomach.

They sign their names on the list of visitors to the crime scene, then follow Erixon to the front door.

'Ready?' Erixon asks with sudden solemnity. 'An ordinary home, an ordinary woman, all those good years then a visitor from h.e.l.l for a few short minutes.'

They go inside, the protective plastic rustles, the door closes behind them, the hinges squealing like a trapped hare. The daylight vanishes, and the sudden shift from a late summer's day to the gloom of the hallway is blinding.

They stand still as their eyes adjust.

The air is warm and there are b.l.o.o.d.y handprints on the door frame and around the lock and handle, fumbling in horror.

A vacuum cleaner with no nozzle is standing on a plastic sheet on the floor. There's a trickle of dark blood from the hose.

Adam's mask moves rapidly in front of his mouth and beads of sweat break out on his forehead.

They follow Erixon across the protective boards on the floor towards the kitchen. There are b.l.o.o.d.y footprints on the linoleum. They've been clumsily wiped, and then trodden in again. One side of the sink is blocked with wet kitchen roll, and a shower-sc.r.a.per is visible in the murky water.

'We've found prints from Bjrn's feet,' Erixon says. 'First he went round in his blood-soaked socks, then barefoot ... we found his socks in the rubbish bin in the kitchen.'

He falls silent and they carry on into the pa.s.sageway that connects the kitchen with the dining and living rooms.

A crime scene changes over time, and is gradually destroyed as the investigation proceeds. So as not to miss any evidence, forensics officers start by securing rubbish bins and vehicles parked in the area, and make a note of specific smells and other transitory elements.

Apart from that, they conduct a general examination of the crime scene from the outside in, and approach the body and the actual murder scene with caution.

The living room is bathed in bright light. The cloying smell of blood is inescapable. The chaos is oddly invisible because the furniture has been wiped and put back in position.

Yesterday evening Margot saw the video of Susanna as she stood in this room eating ice cream with a spoon, straight from the tub.

A plane comes in to land at Bromma Airport with a thunderous roar, making the gla.s.s-fronted cabinet rattle. Margot notes that all the porcelain figures are lying down, as if they were asleep.

Flies are buzzing around a b.l.o.o.d.y mop that's been left behind the sofa. The water in the bucket is dark red, the floor streaked. It's possible to see the trail of the mop by the damp marks left on the skirting boards and furniture.

'First he tried to hoover up the blood,' Erixon says. 'I don't really know, but he seems to have mopped the floor, then wiped it with a dishcloth and kitchen roll.'

'He doesn't remember anything,' Margot says.

'Almost all the original blood patterns have been destroyed, but he missed some here,' Erixon says, pointing to a thin spatter on one strip of wallpaper.

He's used the old technique and has stretched eight threads from the outermost marks on the wall to find the point where they converge the point where the blood originated.

'This is one precise point ... the knife goes in at an angle from above, fairly deep,' Erixon says breathlessly. 'And of course this is one of the first blows.'

'Because she's on her feet,' Margot says quietly.

'Because she's still on her feet,' he confirms.

Margot looks at the cabinet containing the p.r.o.ne porcelain figures, and thinks that Susanna must have stumbled and hit it when she was trying to escape.

'This wall has been cleaned,' Erixon shows them. 'So I'm having to guess a bit now, but she was probably leaning with her back against it, and slid down ... She may have rolled over once, and may have kicked her legs ... either way, she certainly lay here for a while with a punctured lung.'

Margot bends over and sees the blood that has been exhaled across the back of the sofa, from below, possibly during a cough.

'But the blood carries on over there, doesn't it? It looks like it,' she says, pointing. 'Susanna struggled like a wild animal ...'

'And we don't even know where Bjrn found her?' Adam asks.

'No, but we do have a large concentration of blood over there,' Erixon says, and points.

'And there,' Margot says, gesturing towards the window.

'Yes, she was there, but she was dragged there ... she was in various different places after she died, she lay on the sofa, and ... in the bathroom, as well as ...'

'So now she's in the bedroom,' Margot says.

12.

The white light of the floodlamps fills the bedroom, forming blinding suns in the gla.s.s of the window. Everything is illuminated, every thread, every swirling mote of dust. A trail of blood runs across the pale grey carpet to the bed, like tiny black pearls.

Margot stops inside the door, but hears the others carry on towards the bed, then the rustling of their overalls stops.

'G.o.d,' Adam gasps in a m.u.f.fled voice.

Once again Margot thinks of the video, of Susanna walking about with her trousers dangling from one foot as she kicked to get rid of them.

She lowers her eyes and sees that her clothes have been turned the right way and are now piled neatly on the chair.

'Margot? Are you OK?'

She meets Adam's gaze, sees his dilated pupils, hears the dull buzz of flies, and forces herself to look at the victim.

The covers have been pulled up under her chin.

Her face is nothing but a dark-red, deformed pulp. He's hacked, cut, stabbed and carved away at it.

She goes closer and sees a single eye staring crookedly up at the ceiling.

Erixon folds the covers back. They're stiff with dried blood; skin and fabric have stuck together. There's a faint crunching sound as the dried blood comes loose, and little crumbs rain down.

Adam raises one hand to his mouth.

The inhuman brutality was concentrated around her face, neck and chest. The dead woman is naked and smeared in blood, with more stab-wounds and further bleeding beneath her skin.

Erixon photographs the body, and Margot points at a mottled green patch to the right of her stomach.

'That's normal,' Erixon says.

Her pubic hair has started to regrow around the reddish blonde tuft on her pudenda. There are no visible marks or injuries to the insides of the thighs.

Erixon takes several hundred pictures of the body, from the head resting on the pillow all the way down to the tips of her toes.

'I'm going to have to touch you now, Susanna,' he whispers, and lifts her left arm.

He turns it over and looks at the defensive wounds, cuts which indicate that she tried to fend off the attack.

With practised gestures he sc.r.a.pes under her fingernails, the most common place to find a perpetrator's DNA. He uses a new tube for each nail, attaches a label and makes a note on the computer on the bedside table.

Her fingers are limp, because rigor mortis has loosened its grip now.

When he's done with her nails he carefully pulls a plastic bag over her hand and fastens it with tape, ahead of the post-mortem.