I'm Mendel Meade, Anthropologist Second Class. Normally, I roam the depths of our home, the generation ship Chrysalis. I spend my time inoculating against nasty stuff, dealing with problems in various groups and cultures and reporting back—when I can't put it off any longer—to my fellow scientists at the Brainery. But this time, I get ordered back out into the Depths, right away and, most disturbingly, alone. That means leaving my constant companions and right-and-left hand men—well, technically they're fourteen—Darwin and Newton, aka The Terror Twins, aka Oh, No, It's Them, Run—behind. They don't like being left behind. I don't like leaving them alone either, knowing all too well what kind of mayhem they're capable of. But what I find when I get to my assignment—well, I like that even less....