A single mother moves into a new house with her daughter. Soon after the young girl has her first baby tooth fall off, she begins to recount that she is having nocturnal visits by a tooth fairy. It seems the house has a sinister history.

A gang of vicious young punks break into the house of an elderly couple, terrorize, and then murder them. Suddenly, the clocks in the house begin to run backwards, and the dead come back for revenge!

Young poetess Rose Elliot buys a book from a local antique dealer, a diary in Latin of an architect, E. Varelli. She learns of the Three Mothers, and believes her apartment building is one of their houses. She pleads her brother Mark, who is studying musicology in Rome, to come, because she is afraid. Mark's friend Sara reads her letter, which he left behind in class, and discovers the school is run by the Mater Lacrimarum, and is killed for this knowledge. The house of Mater Suspiriorum has already been destroyed, and by the time Mark arrives in New York City, he is investigating his sister's murder.

A New York anthropologist named Professor Harold Monroe travels to the wild, inhospitable jungles of South America to find out what happened to a documentary film crew that disappeared two months before while filming a documentary about primitive cannibal tribes deep in the rain forest. With the help of two local guides, Professor Monroe encounters two tribes, the Yacumo and the Yanomamo. While under the hospitality of the latter tribe, he finds the remains of the crew and several reels of their undeveloped film. Upon returning to New York City, Professor Monroe views the film in detail, featuring the director Alan Yates, his girlfriend Faye Daniels, and cameramen Jack Anders and Mark Tomaso. After a few days of traveling, the film details how the crew staged all the footage for their documentary by terrorizing and torturing the natives. Despite Monroe's objections, the television studio Pan American still wishes to air the footage as a legitimate documentary...