'Operation Fear')[3] is a 1966 Italian gothic horror film directed by Mario Bava and starring Giacomo Rossi Stuart and Erika Blanc.

Written by Bava, Romano Migliorini, and Roberto Natale, the film focuses on a small European village in the early 1900s that is being terrorized by the ghost of a murderous young girl.

Although a complete script was written by Migliorini and Natale prior to the start of production, Bava claimed that much of the film was improvised.

[4] In 1907, Dr. Paul Eswai is sent to the village of Karmingam to perform an autopsy on Irena Hollander, a woman who died under mysterious circumstances in an abandoned church.

The local villagers are accustomed to medicinal practices and superstitions Eswai finds preposterous, and claim that Karmingam is haunted by the ghost of a young girl who curses those she visits.

After Nadienne, the daughter of local innkeepers, is visited by the girl, a ritual to reverse the curse is performed by Ruth, the village witch.

Turned away by Nadinne's father due to her death, Monica and Eswai attempt to get the reluctant villagers' attention by ringing the church bell.

Eswai chases after her through a repeating series of doorways; in his pursuit, he confronts a doppelgänger of himself, after which he is left locked in a room and subsequently spirited out of the villa.

The Baroness stabs her through the chest with a fire poker, but Ruth manages to strangle her to death before dying, thus laying Melissa's soul to rest; Eswai arrives in time to save Monica.

[5] Lucas notes that the script has two possible cinematic antecedents: the 1944 Rathbone/Bruce Sherlock Holmes film The Scarlet Claw, in which Holmes and Dr. Watson are summoned to a small town where a series of murders — the most recent of which is of a woman who bled to death while ringing the local church bell — have been attributed to a ghost, and 1960's Village of the Damned (based on the 1957 novel The Midwich Cuckoos by John Wyndham), in which a group of aliens resembling blonde children menace a village by psychically compelling residents into committing suicide.

[11] Curti noted that La vendetta di Lady Morgan began shooting on 26 July 1965, was submitted to the Ministerial Censorship Commission on 1 October, and was released on 16 December.

[14] According to Blanc, Valeri was not happy with the role due to the need for him to wear a dress, and that Bava would goad his performance by referring to him as "Valeria".

[16] Blanc stated that the cast and crew were only paid for their first two weeks working on the film, and agreed to complete it without pay due to their affection for Bava.

[18] Lamberto Bava described Calcata during this period as "Abandoned, constructed on a mountain of tufa, a material that has crumbled over the centuries" and that around the late 1960s the area "became a kind of hippie community.

[21] Several shots of Melissa were filmed with Valeri performing the actions in reverse, lending an uncanny feel to the character's movements.

The disappearance of her ghost at the end of the film was accomplished by dimming the light that projected Valeri's reflection onto a sheet of angled glass.

[40][41] From contemporaneous reviews, Tom Milne of the Monthly Film Bulletin noted that though "narrative has never been Bava's strong point, but with Operazione Paura he has happily found a story in which atmosphere is everything, and the result is even more splendid visually than Sei Donne per l'Assasino".

[42] Stuart Byron ("Byro") of Variety commented that "every element of light and color has been carefully orchestrated by Bava to achieve a tantalizing and dramatic effect" and "plot details are juggled expertly to achieve needed scare effects" while "there's no attempt to the especial original here - it's just the same old Gothic elements, but handled so skillfully as to revitalize the genre.

"[43][29] The review concluded that "perhaps his pix will remain in the province of buffs, but Bava - whose sole international success was with Black Sabbath - deserves a small but firm niche in film history.

[...] Bava uses the location as a source of found German expressionism, merging the canted windows and seemingly irrational angles of streets and stacked buildings with candy-colored cinematography and pointedly artificial sets.

This contrast between the discovered and the created suggests a porous boundary between reality and subjectivity, the past and present, and the antiquated and modernized.

[45] Bava biographer Tim Lucas described the film as a "mixture of pure poetry and pulp thriller, distinguished by vivid, hallucinogenic cinematography...jolts into the realms of free-form delirium and dementia.

[49] Taste of Cinema observed that "Martin Scorsese called this Bava's best film...probably the most successful realization of Gothic horror-meets-bad-acid-trip.

"[50] Scott Beggs said "This might be Bava’s greatest achievement, and he doesn’t hold out on the lush production design or the trippy camera tricks.

creates such a palpable mood of dread and oppression in its first few minutes and so effectively sustains the momentum until the last frame that it is easy to see why it has cast such a quiet legacy on other filmmakers.

"[53] Pablo Kjolseth of Turner Classic Movies praised the film's visuals, writing: "If you value mood and atmosphere over modern visceral thrills there's a good chance you'll land in the latter camp.

Rich color schemes, crumbling elegant buildings, mist-covered cobble-stoned streets, dusty taverns, swirling spiral stairs, and endless halls with creepy décor and art all help establish a handful of the exteriors and interiors that make the film magical.

[56] In Asia, several productions also feature a spectral young girl with a white bouncing ball, such as Wellson Chin's 1997 film Tamagotchi and the anime series Pokémon, specifically the episodes "Abra and the Psychic Showdown" and "Haunter vs.