His three colleagues had returned a few days ago from their holiday. They had calmly come back to work, and apparently nobody had thought to put two and two together, and thus connect the epidemic with the vacationers. It had been unfortunate that Tanya should have been put under arrest; it was difficult trying to find amusement for Leah so that she would keep out of sight, but still, on the whole, their luck had been good. But it was time for David to go back to work in his office. Gently he detached the mice from his hand, dropped them into their cage, and closed the wire trap. He took his leather pencil case and the keys to his desk from the pocket of his lab coat and laid them on the desk, below the nail on which his wristwatch hung. Carelessly he dropped his lab coat onto the desk and reached for his jacket, then paused, listening. The chatter in the technicians' room suddenly died. In the unnatural quiet sounded a steady march of feet. David turned to meet the probing black eyes of Leader Marley. Just behind him were Dr. Lanza and Officer Magnun. There was no time to conceal his mice, David realized. Shrugging into his jacket, he strode forward without hesitation, a smile on his face, and stretched out his hand. "Leader Marley! This is indeed an honor. If you had only notified us of your visit, we should have been prepared." "Young as ever, I see, Wong." "Thank you, Leader." There was no banter in Marley's eyes, he noted, but he continued amiably. "It has been some years since you have honored us by a visit in person. I'm afraid a laboratory is not a very exciting place, but I'd be honored to show you anything that may be of interest to you." A faint contempt curled Marley's mouth as he glanced around the room. "Nothing to see that I haven't seen before, is there? A lot of test tubes, a bunch of flasks, a mess of apparatus you'd think had been dreamed up by an idiot, and a bad smell. You still keep animals, I notice." He sauntered over to the bench, picked up the cage and looked at the scurrying rodents. David scarcely breathed. Marley only nodded. "Well, mice are mice." He put down the cage and turned away. "These look just like the ones I saw when I was here eight or ten years ago. Same white patch on the forelimbs. I never knew mice could live that long." "But--" began Lanza, bending over to study the mice. "What an amazing memory you have, Leader," said David. "Just as you guessed, these mice are the direct descendants of the ones you saw on your former visit, a special mutant strain. The chief difference is that these are marked with white patches on the _right_ forelimbs, while, as I am sure you recall, the original specimens were marked on the _left_ forelimbs. Odd how these marks run in families, isn't it?" Lanza put down the cage and strolled toward the door as Marley took a last bored look around. "Nothing new here that I ought to see, Lanza?" "No. Nothing new."