It begins with Roger Middleton and Dodger Cheswich. Twins, separated at birth, not entirely human. Telepathic twins, sporadically present in each other's heads and each other's lives. Destined (it seems, possibly by design) to never be long apart.
The astronaut alone in their capsule. The explorer stranded far from home. The one who wakes to the flickering light and failing systems of their underground bunker. The lonely survivor in a ruined world — Last Man Alive.