Ricky looked wonderingly at Gloria and the others who were entering the hut. "Lance, who are all these people? Are they prisoners of Dark too?" "Yes, we're prisoners," Hugh Murdock told him bitterly, with a savage glance at Kenniston. "We're prisoners because your brother sacrificed us all to get back here and save _your_ neck." "Lance, you didn't do that?" Ricky exclaimed in distress. "I had to, Ricky," Kenniston protested. "It meant your life if I didn't." "Of course," Murdock agreed ironically. "What importance are we, compared to saving your young brother's life?" Kenniston spoke slowly, to Murdock and Gloria and the others. "It wasn't merely Ricky's life at stake that made me sacrifice you all. It was more than that. I tried to tell you before, but you wouldn't listen." * * * * * Kenniston went across the hut and brought back the square black medicine-case of his young physician-brother. He opened it, and out of the vials and instruments inside he took a square bottle of milky fluid. "This is what I sacrificed everything to save," Kenniston said simply. They all stared. "What is it?" Gloria asked, puzzled. "It's Ricky's discovery," Kenniston said. "It's a preventative and cure for gravitation-paralysis." Captain Walls, himself an old-time space-man, was first of the group to appreciate the significance of the statement. The captain gasped. "A preventative for gravitation-paralysis? Kenniston, are you _sure_?" Kenniston nodded gravely. "Yes. Ricky had been working on the problem a long time, back in the Institute of Planetary Medicine. He thought he'd found a way to prevent gravitation-paralysis, the most awful scourge of all the outer System, the thing that's doomed so many space-men. But his formula required rare elements found only in the outer planets. "Ricky and I," he continued, "went out there and secured those elements. He made up this formula, and tried it on a gravitation-paralysis case--a space-man who's lain paralyzed for years. The formula was designed to strengthen the human nervous system against the shock of varying gravitations, to re-establish an already damaged nerve-web. And it worked." Kenniston's voice was husky as he concluded. "It worked, and that living log became a man again. The formula was a success. Ricky and I started back for Earth, where he intended to announce the discovery and arrange for its manufacture on a big scale. But, on the way back, Dark's pirates captured us." Kenniston flung out his hand in a tortured gesture. "_That's_ why I went to any lengths to save Ricky's life! It's because Ricky is the only person who knows the intricate formula of this serum. If he were to die, the secret of the cure would die with him. And that would mean that thousands on thousands more of space-men would be stricken into living death by gravitation-paralysis in the future, just as so many thousands of old friends and shipmates of mine have been stricken in the past!"