Jennifer Corvino (Jennifer Connelly), the daughter of a famous actor, arrives at an exclusive girls school in Switzerland, populated by a stern headmistress, taunting classmates, and a psychotic killer stabbing young girls and keeping parts of their bodies. However, Jennifer has an unusual gift, and can communicate with and befriend insects. This and the fact that she has a habit of sleepwalking lead her to entomologist John McGregor (Donald Pleasance), someone with whom she at last has a common interest. Together they start try and solve the recent killings, with the help of the insects.

Dario Argento's first English language film, Phenomena is a daringly surreal exercise in nightmare horror, offsetting the traditional psycho killer plotline with outlandish plot devices, subverting a fairy-tale idyll with pools of corpses, mutant psycho-children, hoards of swarming insects, creepy headmistresses, hallucinatory sleepwalks, corpse-finding insects, Donald Pleasance doing a Scottish accent, heavy metal music, and a chimpanzee weilding a straight razor. Originally released in a heavily editing version, missing some 20 minutes and retitled Creepers, the original, full-length version of Phenomena is thankfully now widely available, & well worth seeking out for fans of the director.