Quicksand — John Brunner

DAW Books, 1976. Paperback, first printing. This 1967 novel tells of a troubled psychiatrist trying to unravel the mystery behind a girl discovered wandering in the woods near a mental hospital. She speaks a language no one understands and doesn't seem to recognize commonplace items such as telephones or automobiles. As the novel progresses, the clues about her origin become more intriguing, even as the psychiatrist's personal life is falling apart.