A fifth of the Earth's population dies at once - why? Epidemic? Weapons of mass destruction? Or are the little green men to blame? In their search for an answer, the heroes - a married couple, a surgeon and a forensic expert - do not exclude even such a reason, because the probability of the others is no greater. Proposing, analyzing and discarding version after version, the heroes gradually come to a completely different question: why are the survivors so lucky? And were you lucky?