A woman named Karen Tandy (Susan Strasberg), who is suffering from a growing tumor on her neck, enters a hospital in San Francisco. After a series of X-rays, two doctors, led by Dr. Jack Hughes (Jon Cedar), find evidence that it is a growing fetus although they don't fully believe it. They advise Karen to undergo surgery to remove the tumor; she agrees despite some anxiety. She seeks the comfort of an old friend and ex-employer named Harry Erskine (Tony Curtis). Erskine is a fortune teller who preys on the gullible to make a living.

Karen and Harry reminisce before Karen reveals her condition. Harry assures her that everything will be fine. Karen spends the night. In her sleep, she utters a phrase that sounds like "pana witchy salatoo" which makes Harry uncomfortable.

The next day, Harry drives Karen to the hospital. He mentions the phrase, but she claims she never heard it before.

As the surgery commences, the lead doctor prepares to remove the tumor by using a scalpel. His hands shake, and he starts to slice his own left hand.

Harry holds a session with one of his regulars who has a seizure and utters the same phrase Karen spoke the night before. Harry calls for an ambulance, but the woman levitates out of the room and falls down the staircase.

Dr Hughes and his companions inform a worried Harry of Karen's condition. Convinced that some kind of black magic is involved, Harry seeks out an old acquaintance named Amelia Caruso (Stella Stevens). She used to be in the psychic business, acting as a medium, and agrees to help him after much debate with her partner MacArthur (Hugh Corcoran). Harry, Amelia, MacArthur, and Amelia's aunt, Mrs. Karmann (Ann Sothern), visit Karen's home, where they hold a seance to draw out the spirit that's causing all the trouble. A violent storm and lightning hinders their efforts. Mrs. Karmann declares that the figure she saw resembled a wooden statue of an Indian. Harry visits aging Dr. Snow (Burgess Meredith), an anthropologist by profession, along with Amelia and MacArthur. They discuss the recent developments; Dr. Snow is initially dismissive and recounts the scarce tales of 400-year-old Indian medicine men with great powers who lived long beforethe white men came. Upon hearing the strange phrase, he deduces it partially to be as "my death foretells my return." Unable to help them directly, he advises them that they should seek the council of the vestigial Indian medicine men now surviving in the remote parts.

Harry visits John Singing Rock, (Michael Ansara) a medicine man who tells him about manitou, spirits who exist in every thing surrounding them. He refuses Harry's plea but later changes his mind and requests $100,000 and tobacco in exchange for his services. Harry and John reach the hospital and draw a circle of sand around Karen's bed in order to limit the spirit using her body. Through Karen, the spirit reveals himself to be an old Native American shaman, Misquamacus; when he says that he is reincarnating himself through the young woman to exact his revenge on the white men who invaded North America and exterminated its native peoples. He further warns John that helping white men such as Harry and Karen is ill advised and against his wishes. John prepares to stop Misquamacus's growing power and calls upon the strength of other manitous, to no avail. the spirit kills one of the male nurses looking after Karen at night and finally claws its way out from Karen's neck in the flesh as a dwarf-sized man. It also reanimates the dead nurse to harm others, but John manages to stop it. In another encounter, the spirit summons an ancient Indian demon by the name of the Lizard of the Tree while managing to erase the sand circle to harm Dr. Hughes on his right hand by transfixing his gaze momentarily. After Harry takes Hughes to the lower levels to treat his wounds, he returns to find the entire floor covered in ice; the receptionist is frozen solid. Harry finds John sitting alone in the room. John explains that the spirit inflicted wounds on his face with surgical instruments. As they are about to leave, they are faced with the spirit caught amidst a snowstorm caused by summoning of another demon called the Star Beast, also known as the Spirit of the North Wind. In the altercation, the frozen receptionist is decapitated as Harry throws a typewriter towards the spirit, which temporarily weakens it, allowing them to escape. John reveals that he won't be able to stop the spirit and Harry comes up with the idea of using the manitous of electrical equipment surrounding them. John reluctantly agrees and proposes he will act as a medium for the machine manitous to manifest themselves. As they are discussing the plan, the entire room shakes with a violent earthquake, which John reveals as the coming of the Great Old One, a powerful satanic demon, through a portal opened by the spirit.

Harry instructs Dr. Hughes to switch on all the machines in the hospital while he and John travel towards the spirit. They find Karen in her bed inside a room filled with space illusion. John tries to channel the machine manitous but is unsuccessful. He accepts defeat, but Harry refuses to give in. He tries to distract the spirit while calling on Karen. Karen gains consciousness and channels the machine manitous to finally defeat the spirit and the Great Old One behind the portal. As the ordeal is over, Harry and Karen are reunited. Harry accompanies John to a cab for the airport, thanking him for his help. John thanks him back and warns that they might meet the spirit once again for though its body maybe destroyed, its ethereal form lives.

• Tony Curtis as Harry Erskine
• Michael Ansara as John Singing Rock
• Susan Strasberg as Karen Tandy
• Stella Stevens as Amelia Caruso
• Jon Cedar as Dr. Jack Hughes
• Ann Sothern as Mrs. Karmann
• Burgess Meredith as Dr. Snow
• Paul Mantee as Dr. McEvoy
• Jeanette Nolan as Mrs. Winconis
• Lurene Tuttle as Mrs. Herz
• Hugh Corcoran as MacArthur

The film was released theatrically by AVCO Embassy Pictures on April 28, 1978, in New York, and May 17, 1978, in Los Angeles.^[2] The film was released on DVD by Momentum Pictures on October 24, 2005. It was re-released on Blu-ray by Anchor Bay Entertainment on March 6, 2007.^[5]

According to the Anchor Bay Blu-ray release, the original negative is lost, and the film had to be restored from alternate elements.

On review aggregator website Rotten Tomatoes, The Manitou has a 40% approval rating based on 10 reviews, with an average rating of 5.1/10.^[6] The staff of Variety wrote, "This bout between good and Satan includes some scares, camp and better than average credits".^[7] Time Out's Derek Adams praised the film's special effects and called the film "a successful excursion, spoiled only by the director's habit of plopping in postcard views of the Golden Gate Bridge instead of exteriors".^[8] Donald Guarisco of AllMovie criticized the film's script and direction but complimented the acting, special effects and ending.^[9] Author John Kenneth Muir wrote the film has "an infectious feeling of fun" despite being "patently absurd".^[4]

Masterton, who wrote the source novel, said he "liked it a lot".^[4]

• The Manitou at IMDb  
• The Manitou at AllMovie
• The Manitou at Rotten Tomatoes
• The Manitou at Box Office Mojo