Camouflage

A million years ago something came out of the deep ocean and began, very slowly, to learn what it was surrounded by. It can be anything: a shark, a seal, a man, and it survives by imitation, accumulating a long and largely uncomprehending education in what humans do to one another. Elsewhere on the same planet another creature of the same kind has drawn a different conclusion, and takes pleasure in the killing. In 2019, a salvage operation off Samoa raises an object from the seabed near Tonga that is impossibly dense, impossibly old and impossibly indestructible, and marine biologist Russell Sutton is given the job of working out what it is. The artefact is a summons, and both creatures come. Haldeman cuts between the changeling's long apprenticeship in humanity, running through the twentieth century in a succession of borrowed lives, and the contemporary work of the research team, gradually tightening the two lines together. It is a lean book by the standards of the subject, more interested in what a mind learns by wearing bodies than in the mechanics of the mystery, and its cold counterpart supplies a genuinely unnerving argument about what a creature without kin might become.