BBC documentary filmmaker Michael Williams (Richard Johnson) is doing a film on the devil in art. He is intrigued by a slide of a painting depicting a Boschian mob pursuing a little girl in white under a falling angel (which reminds him of the death of his wife in a fire) and the devil himself lording over the scene. With his daughter Emily (Nicoletta Elmi), who was traumatized by witnessing her mother's death, her nanny Jill (Evelyn Stewart), and a spunky American producer Joanna (Joanna Cassidy), Williams travels to Spoletto to film the documentary. The psychically-inclined countess (Lila Kedrova)who provided him with slides of the local artwork warns him not to use the painting which she believes to be cursed. Having found the abandoned villa where the painting hangs, Williams goes ahead with the filming while his daughter's behavior becomes more erratic and possessive. After a ghostly flaw on the film necessitates reshoots, Williams discovers a medallion that looks exactly like the one his daughter wears and the countess uncovers startling information about the little girl in the painting (and her tragic death) who may be reincarnated in Emily who has exhibited dangerous animosity towards Joanna and Jill who both have romantic interests in her father.

Former cinematographer Massimo Dallamano (FOR A FEW DOLLARS MORE) follows up his crime films and thrillers (WHAT HAVE YOU DONE TO SOLANGE?) with this lyrical take on the child possession movies of the mid-seventies though he never resorts to Linda-Blairisms to convey the daughter's behavior. The wintry London and autumnal Spoletto locations are lovingly captured by Franco Delli Colli and Stelvio Cipriani's score largely eschews traditional horror music (the few instances of it anticipate his work with Goblin on SOLAMENTE NERO [1978]) in favor of variations on a romantic theme that infuse the story with a sense of inevitable tragedy.

The "Perché?!" subtitle of the film's title reappears at the end of the film echoing the ghost child's question before the final fade out (neither the subtitle nor the end narration are included in the English version).