Victor Buono gives a chilling performance as Leo Kroll, a worker in a Boston hospital who has a propensity for strangling young nurses. Like Norman Bates in Psycho, Leo has an extremely unhealthy mother fixation. When Mom (Ellen Corby suffers a heart attack and Clara (Jeanne Bates), a young and attractive nurse, is assigned to care for her, Leo's hormones start to rage. On one hand Leo is attracted to Clara, but he is also jealous of her, fearing that she has replaced him in his mother's affections. Leo proceeds to go on a killing spree, targeting young and attractive nurses. But Leo's downfall is imminent; he is a collector of kewpie dolls, and mistakenly leaves one behind at the scene of one of his murders.