The Case of the Bloody Iris (1972)

Beautiful young model Jennifer Lansbury and her goofy friend Marilyn Ricci move into a swanky high-rise apartment after the previous tenant gets brutally murdered. Pretty soon Jennifer is being stalked by the mysterious killer. Probable suspects include a predatory lesbian neighbor, a weird old woman and her deformed son, and even the building's handsome architect who suffers from a severe blood phobia.