A solid new interpretation of the short-lived but oft-analyzed collaboration between Freud and Jung, in which the mysterious Sabina Spielrein figures prominently. Using Spielrein's correspondence and journals--discovered in the 1970's and first appearing in Aldo Carotenuto's A Secret Symmetry (1982)--Kerr traces a fascinating, credible web of influence and cross-fertilized ideas that he weaves skillfully into a record of psychoanalytic history. Spielrein--a young, neurotic Russian who was in Zurich to receive psychoanalytical treatment and attend medical school--was Jung's patient and, later, his lover; but even though a falling out prompted her to move to Vienna to become a Freudian, the ties between analyst and patient remained strong--so much so that Kerr contends that Spielrein can be seen as the model for Jung's concept of the ``anima'' (the female part of the male psyche). By chronicling this progression of events from 1904 to the final, fragmentary evidence of the pair's contact in the 1920's--before Spielrein returned to Russia in hopes of building a psychoanalytic movement, only to run afoul of Stalin-- the depth to which Jung and Spielrein influenced each other's thinking appears clear. Spielrein left her mark on Freud as well, in the form of a 1912 essay positing a link between an individual's desire for death and the sexual instinct. Most important to Kerr's history, however, is the intense interplay between Jung and Freud, with the decay of their mutual admiration into animosity and recrimination hastened by Spielrein's presence. More attentive to Jung's side of the equation, perhaps, but still a neat, substantial piece of psychoanalytic puzzle-solving, provocative and eminently readable.