"Can't it wait?" The protest came from Marie LeGarde. "Can't you see that the poor girl is chilled to death?"

"Can't you see that I am too?" I snapped. It was a measure of the mood I was in when I could bring myself to speak like that to Marie LeGarde. "Coming, Miss Ross?"

She came. I was taking no chances this time, so I carried with me the big searchlight with its portable battery and another torch, and gave the stewardess an armful of bamboos. When we had reached the top of the hatchway steps she waited for me to lead the way, but I told her to walk in front. I wanted to watch her hands.

The snow was easing now, the wind dropping and visibility just a little improved. We walked the length of the antenna line, angled off a little way north of east, setting down an occasional bamboo, and were at the plane within ten minutes of leaving the cabin.

"Right," I said. "You first, Miss Ross. Up you go."

"Up?" She turned towards me, and though the big searchlight lying on the ground was no help in letting me see the expression of her face, the puzzled tone of her voice was exactly right. "How?"

"Same way as you did before," I said harshly. My anger was almost out of control now, I couldn't have restrained myself any longer. "Jump for it."

"The same way – " She stopped in mid-sentence and stared at me. "What do you mean?" Her voice was only a whisper.

"Jump for it," I said implacably.

She turned away slowly and jumped. Her fingers didn't come within six inches of the sill. She tried again, got no nearer, and on her third attempt I boosted her so that her hands hooked over the sill. She hung there for a moment, then pulled herself up a few inches, cried out and fell heavily to the ground. Slowly, dazedly she picked herself up and looked at me. A splendid performance.

"I can't do it," she said huskily. "You can see I can't. What are you trying to do to me? What's wrong?" I didn't answer, and she rushed on. "I – I'm not staying here. I'm going back to the cabin."

"Later." I caught her arm roughly as she made to move away. "Stand there where I can watch you." I jumped up, wriggled inside the control cabin, reached down and pulled her up after me, none too gently, and without a word I led her straight into the galley.

"The Mickey Finn dispensary," I observed. "An ideal quiet spot it is, too." She had her mask off now, and I held up my hand to forestall her as she opened her mouth to speak. "Dope, Miss Ross. But of course you wouldn't know what I'm talking about."

She stared at me unblinkingly, made no answer.

"You were sitting here when the plane crashed," I went on. "Possibly on this little stool here? Right?"

She nodded, again without speaking.

"And, of course, were flung against this front bulkhead here. Tell me, Miss Ross, where's the metal projection that tore this hole in your back?"

She stared at the lockers, then looked slowly back to me.

"Is – is that why you've brought me here – "

"Where is it?" I demanded.

"I don't know." She shook her head from side to side and took a backward step. "What does it matter? And – and dope – what is the matter? Please."

I took her arm without a word and led her through to the radio cabin. I trained the torch beam on to the top of the radio cabinet.

"Blood, Miss Ross. And some navy blue fibres. The blood from the cut on your back, the fibres from your tunic. Here's where you were sitting – or standing – when the plane crashed. Pity it caught you off balance. But at least you managed to retain your hold on your gun." She was gazing at me now with sick eyes, and her face was a mask carved from white papiermache. "Missed your cue, Miss Ross – your next line of dialogue was 'What gun?'. I'll tell you – the one you had lined up on the second officer. Pity you hadn't killed him then, isn't it? But you made a good job of it later. Smothering makes such a much less messy job, doesn't it?"

"Smothering?" She had to try three times before she got the word out.

"On cue, on time," I approved. "Smothering. When you murdered the second officer in the cabin last night."

"You're mad," she whispered. Her lips, startlingly red against the ashen face, were parted and the brown eyes, enormous with fear and sick despair. "You're mad," she repeated unsteadily.

"Crazy as a loon," I agreed. Again I caught her arm, pulled her out on to the flight deck and trained my flashlight on the captain's back. "You wouldn't, of course, know anything about this either." I leaned forward, jerked up the jacket to expose the bullet hole in the back, then stumbled and all but fell as she gave a long sigh and crumpled against me. Instinctively I caught her, lowered her to the floor, cursed myself for having fallen for the fainting routine even for a second, and ruthlessly stabbed a stiff couple of fingers into the solar plexus, just below the breastbone.

There was no reaction, just no reaction at all. The faint had been as genuine as ever a faint can be and she was completely unconscious.

The next few minutes, while I sat beside her on the front seat of the plane waiting for her to recover consciousness, were some of the worst I have ever gone through. Self-reproach is a hopeless word to describe the way I swore at myself for my folly, my utter stupidity and unforgivable blindness, above all for the brutality, the calculated cruelty with which I'd treated this poor, crumpled young girl by my side. Especially the cruelty in the past few minutes. Perhaps there had been excuse enough for my earlier suspicions, but there was none for my latest actions: if I hadn't been so consumed by anger, so utterly sure of myself so that the possibility of doubt never had a chance to enter my mind, if my mind hadn't been concentrated, to the exclusion of all else, on the exposure of her guilt, I should have known at least that it couldn't have been she who had jumped down from the control cabin half an hour ago when I had rushed up the aisle, for the simple but sufficient reason that she had been incapable of getting up there in the first place. Quite apart from her injury, I should have been doctor enough to know that the arms and shoulders I had seen while attending to her back that evening weren't built for the acrobatic performance necessary to swing oneself up and through the smashed windscreen. That had been no act she had put on when she had fallen back into the snow, I could see that clearly now; but I should have seen it then.

I still hadn't got beyond the stage of calling myself by every name I could think of when she stirred, sighed and straightened in the crook of the arm with which I was supporting her. Her eyes opened slowly, focused themselves on me, and I could feel the pressure on my forearm as she shrank away.

"It's all right, Miss Ross," I urged her. "Please don't be afraid. I'm not mad – really I'm not – just the biggest blundering half-witted idiot you're ever likely to meet in all the rest of your days. I'm sorry, I'm most terribly sorry for all I've said, for all I've done. Do you think you can ever forgive me?"

I don't think she heard a word I said. Maybe the tone of my voice gave her some reassurance, but it was impossible to tell. She shuddered, violently, and twisted her head to look in the direction of the flight deck.

"Murder!" The word was so low that I could hardly catch it. Suddenly her voice became high-pitched, unsteady. "He's been murdered! Who – who killed him?"

"Now take it easy, Miss Ross." My heavens, I thought, of all the fatuous advice. "I don't know. All I know is that you had nothing to do with it."

"No." She shook her head tiredly. "I don't believe it. I can't believe it. Captain Johnson. Why should anyone – he hadn't an enemy in the world, Dr Mason!"

"Maybe Colonel Harrison hadn't an enemy either." I nodded towards the rear of the plane. "But they got him too."