Charles Render is a shaper, one of a small number of psychotherapists qualified, by his granite will and ultra-stability, to use the extraordinary device that enables him to to participate in, and control, his patients' dreams. But this is a dangerous therapy for the therapist and only his armour-plated integrity protects Render from too deep an involvement in the mental worlds of the damaged people he seeks to help. But then, Eileen Shallot, another therapist who is blind, asks him to help her 'see' by transferring from his mind to hers a world of colour and light. Render agrees but suddenly finds himself obsessed with Eileen and drawn into fantasies which, she controls.