She shoots me a nasty glare, then seems to repent, and nods apologetically. "Antigenic shift," she says, starting again. "It’s like ..." She closes her eyes as she searches for an analogy suitable for bonedomes like me. "As part of the immune response, the body produces these things called antibodies. You can think of them like cops, okay?" I glimpse Argent’s faint grin, but I ignore him.