I Will Fear No Evil
Robert A. Heinlein
 The story takes place about 2015 AD, against a background of an overpopulated Earth, whose dysfunctional society is clearly an attempt to extrapolate into the future the rapid social changes taking place in the U.S. during the 1960s. Ancient billionaire Johann Sebastian Bach Smith is dying, and wants to have his brain transplanted into a new body. Smith advertises an offer of a million dollars for the donation of a body from a brain-dead patient. Coincidentally, his beautiful young female secretary, Eunice Branca, is murdered, so her body is used, since Smith never thought to place any restriction on the sex of the donor. He is rechristened Joan Eunice Smith. For reasons never made clear, Eunice's personality continues to co-inhabit the body. (Whether Eunice's personality is real or a figment of Johann's imagination is addressed but never fully resolved in the novel.) Joan and Eunice agree never to reveal her continued existence, fearing that they would be judged insane and locked up. The two of them speculate that it may have something to do with the supposed ability of animals to remember things using RNA rather than the nervous system. (At the time the book was published, biologist J.V. McConnell had done a series of experiments in which he taught a behavior to flatworms, ground them up, and fed them to other flatworms, which supposedly exhibited the same behavior. McConnell's experiments were later discredited, but ideas drawn from them were used in science fiction by several authors, including Heinlein, Larry Niven, Joe Haldeman and Dean Koontz.) However, Joan and Eunice decide that this possible explanation is irrelevant, and near the end of the book, a third personality, that of Joan's new husband, joins them by means that can only be explained via delusion, religion or mysticism, not science.