I acknowledged, then asked without preamble: "What news from Uplavnik?"

"Two things, Dr Mason." Hillcrest had taken the microphone over from Joss, and, even through the distortion of the speaker, his voice sounded strange, with the flat controlled unemotiona-lism of one speaking through a suppressed anger. "Uplavnik has been in touch with HMS Triton—the carrier coming up the Davis Strait. Triton is in constant communication with the British Admiralty and the Government. Or so I gather.

"The answers to your questions are these. Firstly, the passenger list from BOAC in America is not yet through, but it is known from newspaper reports that the following three people were aboard: Marie LeGarde, the musical comedy star, Senator Hoffman Brewster of the United States and a Mrs Phyllis Dansby-Gregg, who appears to be a very prominent London socialite."

I wasn't greatly excited over this item of news. Marie LeGarde had never been a suspect. Mrs Dansby-Gregg—and, by implication, Helene Fleming—had never had more than a faint question mark against their names, and I had already come to the conclusion that it was long odds against the man who was, or purported to be, Senator Brewster being one of the killers.

"The second thing is this. The Admiralty cannot or will not say why the plane has been forced down, but I gather there must have been a most vital reason. Uplavnik suggests, on what basis I cannot say, perhaps it is officially inspired, that some person aboard the plane must have been in possession of something of the utmost importance, so important that complete secrecy was vital. Don't ask me what it was. A microfilm, a formula, something, perhaps, only committed to memory—it sounds fanciful, but that's all we can guess at. It does seem likely that Colonel Harrison was in possession of it."

I looked at Jackstraw, and he at me. The man who had so recently knocked me out had been desperate all right. I knew then what I had subconsciously known all along, that I was dealing blindfolded against a man—or men—far cleverer than myself. They knew that Joss couldn't possibly have hoped to repair the RCA. They knew, therefore, that I must have been talking direct to Hillcrest. They knew, because I had told them, that the eight-watt radio we had with us had a range of not more than 150 miles under normal conditions, so that the chances were high that Hillcrest was actually speaking from the IGY cabin—or a point even nearer. I had also told them that Hillcrest and his four companions wouldn't be returning from their field trip for another two or three weeks, so that this premature return could only be accounted for by some unforeseen and extraordinary event. It wasn't hard to guess what that event must have been. That I should ask Hillcrest to find out the reason for the crash followed inevitably, but what was not inevitable, what pointed most clearly of all to the shrewdness of the killers, was their guess that whoever knew the reason for the crash would be most reluctant to go into specific detail: and they had robbed me of the only clue that might have helped me discover what that detail was and so also, I felt sure, the identity of the killers. But the time was far past now for crying over spilt milk.

I pressed the switch to Transmit'.

"Thank you. But please radio Uplavnik again, emphasise desperate urgency of finding out crash reasons. . . . How far behind do you estimate you are now? We have made only twenty miles since noon. Cold extreme, bad radiator trouble. Over."

"We have made only eight miles since noon. It seems—"

I threw the switch over.

"Eight miles?" I demanded harshly. "Did I hear you say eight miles?"

"You heard." Hillcrest's voice was savage. "Remember the missing sugar? Well, it's turned up. Your fine friends dumped the whole bloody lot into the petrol. We're completely immobilised."