This is how it starts, among the closed circles of the marooned, the shipwrecked, the besieged: jealousy, dissention, a breach in the groupthink walls. Then the entry of the foe, the murderer, the shadow slipping in through the door we forgot to lock because we were distracted by our darker selves: nursing our minor hatreds, indulging our petty resentments, yelling at one another, tossing the crockery.