Tiger Tiger Book II — Robert Shaw

After wandering around looking for someone on this strange world for over a year; Rab makes a home in a remote valley where he lives content, if lonely, until the locals turn up. They are not friendly; they are here to hunt him and he has to escape down river, followed all the way by the last one intent on killing him. After rescuing his pursuer from certain death he keeps him alive and befriends him calls him Eric; only to have him disappear just when they have found a new home and are starting to communicate. He is left on his own to start again; to build a home, when the weather takes a turn for the worse and everything changes.