"Don't pretend," Snow said. "I know. The last two letters from Ted convinced me something was wrong. He never wrote those letters."

I thought of Baxter's agents sweltering to turn out perfect facsimiles of children's letters, all for nothing. I sighed, and determined to make one last effort to keep the secret a secret. "You're imagining things. Sometimes, when a person is in an alien environment—which you must admit a strange planet is—their outlook changes a bit."

She was staring at me, her eyes disconcertingly steady, just waiting for me to complete my lie, hardly listening to me. I gave it up and stopped. Snow, seeing I was through, unclasped her handbag and handed me a letter.

I read it through. When I was finished, I looked at her with what I hoped was a noncommittal expression.

"See what I mean?" said Snow. "Three l's in really, and terrible spellings of ancient and Martian. But words like ruins and civilization come through perfectly. It's an obvious attempt on the part of someone to deceive me. I just know something's wrong. That's why I drained my savings account and took this flight. I've got to find out what's happened."

"You could have gone to the police." I suggested lamely.

"I did." Snow's voice was cold and flat. "They laughed at me, said I was imagining things. I don't really blame them; all I have to go on is a hunch. That, plus the fact that Ted didn't say anything in our special code."

I closed my eyes and groaned. She would have a special code with her brother! "Sure he didn't simply overlook it?" I tried.

Snow's face was solemnly earnest. "In one letter, by the longest stretch of the imagination, possibly. But not two in a row." She leaned forward, her eyes housing desperation. "So when I learned that you, an Amnesty-bearer, were aboard, I just knew it had to be connected with whatever happened to Ted. There is something wrong, isn't there!"

I hesitated, wondering what to do. This thing was a tightly kept secret, one which I'd sworn to keep. On the other hand, Snow had the most devastating blue eyes. I shifted in my position and felt cold metal bump lightly against my chest beneath my blouse. I'd forgotten about the Amnesty. Hell! I was the most influential, powerful person in the universe, wasn't I? If I wanted to plaster the secret across the face of the moon, no one had the authority to say no. Not even Baxter, however purple he might turn at the idea, could tell me not to do anything! And hadn't I been picked by the Brain? Didn't that mean that my instincts in this thing would be the correct ones?

I took one more look into her deep blue eyes and decided that even if it was the most disastrous thing to do, I was going to tell her the truth.

"It depends on what you mean by wrong," I said.

Snow's brow crinkled. "Then the boys have vanished?"

I nodded, and she went deathly pale. "But don't worry," I said quickly. "It may not be as bad as we think."

"What!" she gasped. "Fifteen little boys missing on an alien planet, and it may not be bad? Are you out of your mind?"

"If you'll calm down a bit and let me explain." I suggested.

Snow leaned back in her chair and folded her arms. "Go ahead," she said resignedly.

I told her about my being picked up at work by the Security Agents, of my meeting with Baxter, and of my investigation of Phobos II. She listened that far in silence, then could hold back no longer.

"But what did you find in those lockers? And what does the takeoff thrust and the dehumidifying system have to do with the boys' disappearance?"

I smiled reassuringly at her. "Listen, Snow. Baxter, myself, and probably you, too, have one reaction in common about the boys' vanishment from a ship in space. Our very first word on the subject is an incredulous 'Impossible.' Of course, we're using it in the colloquial sense; that of 'I don't believe it!' But if we take it in its literal sense, we'll be absolutely correct. Such a thing is impossible."

Snow opened her mouth, but I shushed her unspoken words with a wave of my hand. "I know, you're about to spout something about magnetic grapples and mid-space boardings, or even about long distance teleporting rays—none of which have as yet, so far as we know, been invented—or some such rot. But what are the arguments against these two solitary possibilities?

"As to the first; Anders, the pilot, would surely have noticed another ship in his vicinity. The meteorite warnings would have begun jangling when the ship was still hundreds of miles away. And if it could, somehow, evade the signalling devices, Anders would still have heard the ship make contact. You can't drive up in a spaceship big enough to hold at least fifteen normal-sized boys, besides your own crew, and just not be noticed!

"So we come to the second, and only other, possibility: Were the boys kidnapped by some ultrasuper teleportation beam? The answer, of course, is a resounding, 'Hell, no!'"

Snow frowned. "Why?"

"The thrust, Snow, that's why. If that weight were suddenly removed from the ship—boys of Space Scout age usually run to an average weight of one hundred pounds, or, in this case, a total of about fifteen hundred pounds—if that weight had suddenly become missing, then Anders' fuel consumption, remaining the same but with less mass to thrust, would have made him overshoot Earth. This, however, did not happen. In fact, the gauges in the pilot's compartment plainly show that the ship's mass was, on landing, within a fraction of an ounce of its takeoff mass. Therefore, no mass at all was lost in space except that expended by the consumption of fuel."

Snow shook her head, bewildered. "But that doesn't make sense!" she cried. "If they weren't taken off the ship in space, and they weren't aboard her when she landed, then—" All at once, she got it, and sat back with a sharp gasp.

"Exactly," I said. "They never even left Mars."

"But you said that this man Anders had seen to it that they were all aboard before takeoff."

"Which I have no doubt he did. But the civilian mind skips a few details when it thinks over his report. They see him look at the boys, nod, then go up front and press the starter button. It doesn't happen quite that simply. There are a lot of other things to be done. Anders had to go into the pilot's cabin, strap himself in place, check the guages which showed his course, mass, fuel supply, thrust control, oxygen-nitrogen mixture, and a million and one other things. He had to check the last and most important dial examined before takeoff; the one which told him that each of the fifteen takeoff racks in the ship were occupied."

"But—" Snow cut in, bewildered, leaning forward.

"Let me finish." She set her mouth and sat back again. "He had to know that, because takeoff thrust on a human being not snugly in his padded rack would probably squash him to pieces against a bulkhead. So there had to be something in those racks in order to fool Anders into thinking that the scouts were still aboard; something which, by the time Anders had maneuvered the ship into its flight vector, would be gone without leaving a trace, or not much of a trace, unless one were actually looking for it."

"What?" asked Snow, fascinated.

"Ice," I said. "Hunks of ice in every one of the fifteen bunks. Ice which the temperature control unit would commence to melt immediately."

"But that would mean ice blocks of hundred-pound weights! They couldn't melt so fast. Wouldn't Anders be likely to come back to the racks and find them still there?"

"Not," I said, "with the efficiency of the temperature control system. Sharp deviations from comfortable levels in a spaceship can be disastrous. So the thermostat in the ship is set for a rigid fifty-five degrees, and it's built to keep the interior heat at that level. Put fifteen-hundred pounds of ice on board, and the heat in the rack cabin goes up, trying to get the temperature back to its correct level. The ice, lying there melting, absorbs the heat swiftly. So more heat is pumped into the room. Well, figure fifteen minutes before all the ice was liquified. More than enough of a margin of safety."

"Safety for whom?" Snow asked.

"For whoever didn't want Anders finding any evidence of how the disappearance was accomplished. About an hour passed between takeoff and the time he checked the cabin. You must remember that Anders had to maneuver the ship free of Mars' gravity, set his course for Earth, and then make a final check of all his equipment before going back into the ship proper. That takes plenty of time."

"But how could you figure this out?" Snow asked, her eyes wide with interest. "And where did the ice come from?"

"From the night side of Mars," I said. "Where the temperature drops below zero as soon as the sun has gone down. Remember, the ship was in a landing berth, and had just been prepared for a takeoff. The technicians would have moved away to be clear of the blast. In fact, they'd all be inside their shacks, having coffee against the chilly weather they'd been exposed to. All it took was someone bright enough to get hold of the water tank, and to spray the water into any handy container where it would freeze solid in a few seconds. Then the chunks of ice were substituted for the boys in the bunks, and Anders took off with no one but himself on board."

"You reasoned this out?" Snow said, incredulously. "How?"

"My gift for spotting, which I told you about. Once I knew that the boys could not have been kidnapped from space, and that something had to be making up for their mass aboard the Phobos II, I tried to think of where this something could be kept. It wasn't in the open, nor in any of the storage space. Therefore, it had to be within the bulkheads. But what could go within the bulkheads? Only water which had been taken from the air to keep the humidity down. And yet this water had to remain—without a container, mind you—in the fifteen racks at takeoff time so that Anders' dial would register them as all being securely in place before he pressed the starter. So in what form could water sit on a bunk without a container?"

Snow smiled helplessly, "Ice, of course. You make it sound almost idiotically simple." Then her face fell. "But it's only a theory, isn't it! Or is it?"

I shrugged. "It seems borne out by a few things, Snow. When I entered the Phobos, I checked beneath the canvas covering on one of the takeoff racks. There was grit there, which is a little unusual on a military vessel, with their one-track-mindedness about things being spic and span. And water running through canvas, taking along the dirt that even a military white-glove inspection can't find, leaves behind a residue of grit."

"It still doesn't seem enough," she said wistfully, as if begging me to prove my theory correct for her peace of mind. I was glad to oblige.

"There's more. Water weighs in at 62.4 pounds per cubic foot. So, fifteen hundred pounds of water would occupy approximately twenty four cubic feet; the exact surplus found aboard the Phobos II, in the bulkhead tubing."

Snow looked startled, but still unconvinced. "To kidnap fifteen boys, without Anders noting even the slightest sign of a struggle or disturbance...."

I nodded. "Right. It is odd, isn't it! This bothered me, too, until I checked the contents of those storage lockers."

"Oh. I'd forgotten about that!" she exclaimed. "What did you find?"

"Roughly, without going into precise itemization, there were bottles of space sickness capsules, clean handkerchiefs, toothbrushes, packets of soap and the like."

"And the like?" Snow remarked. "What likeness is there between those things?"

I smiled happily, and told her, simply, the clinker I'd spotted at once on seeing those items: "They're all items which small boys hate with almost apocalyptic fury. But I did not find such things as jackknives, candy, chewing gum—Shall I go on?"

"You mean that whoever kidnapped the boys took along the things which the boys wanted?" she asked, her lovely voice making an unbelieving squeak on the last word.

"I mean," I said softly, "that I believe the Space Scouts left the Phobos II of their own free will."

---