'Can it serve a useful purpose? This matter is now outside our hands.'

It may,' returned Thirty. 'n.o.body knows about this prisoner-yet.' He turned to the German, who was regarding him stolidly. 'You know that after you are handed over it will only be a matter of hours before you are shot?' he inquired, sharply.

Of course. People who undertake our work must be prepared for that.'

Thirty ignored the oblique reference to his own activities. 'You would, I imagine, be interested in saving your life?'

'Naturally.'

'What are you getting at?' demanded Biggles.

'Please,' implored Thirty. He returned to the prisoner. 'I was thinking we might exchange a life for-a life,' he said in a low voice.

'You mean-exchange this fellow's life for Forty's?' asked Biggles.

'Yes.'

'But you can't do that sort of thing.'

I'd do anything to save my brother-anything,' declared Thirty pa.s.sionately.

The German started slightly at the words 'my brother'. Ah!' he exclaimed softly.

'You'll get yourself shot before you're through-in fact, all of us,' Biggles told Thirty grimly.

'Nothing of the sort. No one need know of this.' Thirty again addressed the prisoner. 'If we are going through with this we must understand each other,' he said. 'I am not asking you to betray your side. You need say no more than is necessary for me to save my brother's life. Neither side would gain anything if you both died; they would gain an advantage if you both lived. Is my brother a prisoner?'

'No.'

'Where is he?'

'No one knows. He escaped.'

'Did he know that his reason for being in your country was known to you?'

'Yes.'

'But you don't know where he is now?'

'We a.s.sume that he will make for the landing-ground where I was picked up.'

And that is why the soldiers are there-to arrest him when he comes.'

'So.'

And what part were you to play in this?'

'None. A means was provided for the department for which I work to place a man within your lines. I was chosen. The choice was not mine. I was a tutor of English at Heidelberg University.

Also, I am able to fly.'

Thirty thought swiftly. It struck him that the man standing before him could not be known to the soldiers, or he, Thirty, would have been taken for an escaped prisoner when he came face to face with the German by the hedge. He realized now that the German soldier was prepared to see a British officer there, but could not recognize him personally. He proceeded to confirm it.

'The troops at the landing-ground do not know you by sight?'

'They have never seen me. I have never seen them.' 'They mistook me for you?'

'That is what occurred to me at once when you reported that you had seen a German soldier at close quarters, and he ignored you.'

'They were expecting you?'

'They had been warned, of course, that a man wearing a British uniform would be there, or would shortly arrive; otherwise my life would have been in danger.'

Thirty could now understand the whole situation. He went on swiftly.

'Were they told to expect one only, or how many?' I do not know that.'

Thirty felt that the man was speaking the truth.

'You say they are waiting for my brother. He will be in British uniform. How were they to know which was you, and which was him? Why did they not take me for him?'

I can only suppose that when they saw a man strolling along the hedge in broad daylight they did not imagine that it was an escaped prisoner. Therefore it must be me. They know now that I have gone. When another comes, perhaps creeping up the hedge, they will know it is the man they seek.'

Ah! I understand. Do you know of the other landing-grounds?'

'We know everything. Your brother was suspected. A valuable British officer was placed in his cell with him-also a microphone was hidden in the wall.'

Thirty caught Biggles's eyes. 'We were afraid of that.'

Biggles shook his head. 'Really, Thirty, you can't go on with this,' he said. 'It's against all -'

I don't care what it's against. Do you want to see Forty shot?'

Of course not.'

If no one ever knew about this, don't you think it would be a fair exchange?'

'Possibly.'

Thirty again turned to the German. 'It will save you the indignity of being searched if you will tell me truthfully whether you have any doc.u.ments on you to prove your ident.i.ty.'

The German smiled faintly. 'And me coming into the British lines? No.'

A pa.s.sword, perhaps?'

The German hesitated.

'To withhold it will mean your death, and the death of another.'

'The pa.s.sword is- Vorgehen.'

Advance?'

'So.'

Thirty turned to Biggles. 'That's all I want to know.'

'But what are you going to do, in heaven's name?' I'm going back to the landing-ground.'

'But it's trapped! It's stiff with soldiers.'

I am quite aware of it. If I'm not back here in three hours you must take any steps you think proper. Look after the prisoner for me during that time. Maybe he will give you his parole.'

And then?'

Thirty looked Biggles straight in the eyes. 'If I manage to get back here with Forty I shall allow Captain Forsyth to take a flight in the machine I come back in-which will be one of the F.E.'s.'

'You'll let him go?'

'What else?'

Biggles raised his hands, palms outward. 'I've nothing more to say,' he said in tones of resignation. I shall be the one who is shot before this affair is finished.'

Another thought came into Thirty's mind. 'How did you propose to get back to your side of the lines when you had done what you came to do?'

I hoped to be able to borrow an aeroplane.' 'Didn't you fear that you would be shot down by your own machines?'

'My headquarters were not likely to overlook such an elementary point,' was the calm reply.

'What were you to do?'

The German took a large yellow silk handkerchief from his pocket. 'I should have tied that on the tail of the machine,' he explained.

'Your Jagdstaffeln know that mark?'

'Yes.'

'By gosh! That's worth knowing,' put in Algy.

The German shook his head. 'The knowledge is of little service to you, otherwise I should not have told you. The colour and the position from which it is exposed are changed every week.'

Thirty took the handkerchief. 'I'm going now,' he said.

'Well, good luck,' replied Biggles.

Aren't you going to take me?' cried Rip.

'No.' Thirty walked towards the door. As he did so it opened and Major Raymond came in.

Ah! Here you all are,' he said cheerfully. His eyes swept the room and came to rest on the stranger.

Thirty felt that the room was spinning round him. He could think of nothing to say.

Biggles came to his rescue. 'Allow me to introduce a friend of mine,' he said, casually. '

Captain Forsyth of the Buffs.'

Chapter 18.

Thirty Goes Back To Thirty's unutterable relief the major merely nodded. "Morning, Forsyth,' he said.

Then, to Thirty, 'Where are you off to?'

I'm just going to see what I can do with a Fee, sir,' answered Thirty, truthfully.

I see. Well, don't let me stop you. I was just pa.s.sing, so I thought I'd look in. You've nothing to add to what you told me on the telephone this morning?'

'No, sir. Everything went off all right.'

'Well, from a conversation I have just had on the telephone' (the major's voice took on a meaning tone), I should hardly say that. But all's well that ends well, that's the chief thing.'

'You don't want me again for anything, sir?' 'No-not at present.'

'Then I'll be getting off in case the Fees are wanted.'

'Yes, I'll be getting along, too. Just one thing. Will you fellows dine with me at Wing Headquarters tonight?'

Biggles answered for all of them. 'Thanks very much, sir, we'd like to.'

'Fine; then that's settled. See you later.' The major hurried away.

Biggles wiped imaginary perspiration from his brow. 'These shocks will be the death of me,' he declared, sadly.

Thirty took a last look round the room. In his heart he did not expect to see any of the faces again. But he did not say so. With a brief 'Look after Forsyth' he turned on his heel and walked quickly to the nearest Fee, which the mechanics had just finished refuelling.

He tied the handkerchief to the tail and then climbed into the c.o.c.kpit.

His face was set in hard lines as he took off. He felt that he had reached the limit of something-he was not sure what. The crucial moment of his life was at hand. The next hour would decide his fate, and Forty's fate. That was all that concerned him. Hitherto he had regarded the war as something impersonal; something which was best regarded in the abstract. Now the war meant him and Forty. For the first time he began to perceive what war really meant; he felt the relentlessness of it-the ruthlessness, the waste, the cruelty, the incredible folly of it. It gave him a shock to realize that he did not really know what everybody was fighting for. Something about Belgium . . . Freedom. He pictured the face of the man who had called himself Forsyth; he was quite young, not much older than himself; he did not look as if he wanted to make a slave of anybody; a few months ago he was probably playing rugger; to-morrow he might be riddled with bullets.

Yet only a short while before he, Thirty, had been impatient to get to the war. How silly it all was. A wave of despondency swept over him.

He was, of course, tired; more tired than he knew; yet, strangely enough, he was not conscious of it; on the contrary, he felt curiously alert. His brain thought clearly, intensely. It seemed to be racing inside his head. Every nerve in his body was keyed up, quivering like a taut wire in a gale. He could almost feel them vibrating. They made his hands tremble.