A competent, mildly diverting debut for psychiatric social worker Dr. Sara Marks, working at a Washington, D.C. mental clinic with homosexual colleague Frank Thomas and various supervisors. The murder victim, found floating in the Potomac: Sara's anorexic, promiscuous patient Helena Morgan--who had fallen in love with Frank's patient Harry Hopper, subject to spells of bizarre behavior. (Harry even got her a job at the Caliban Cafe, owned by his father and old army buddy Maury Roden.) Did Helena die because she fell out of love? Or because of something going on at the Cafe? Sara suspects the latter--especially after a second killing. But there are innumerable family-therapy sessions before her explorations and intuitions turn up the prosaic solution. Of special interest to case-history enthusiasts; limited appeal for others.