When Grandma Eunice gives Malcolm a strange bottle that she "won" during the 1939 World's Fair, it turns out to contain the ectoplasm of the performer that she tricked--so if Malcolm wants to keep his bottle he is going to have to figure out how to evict this stubborn ghost.

Ten-year-old Malcolm and his best friend Dandy, armed with a ghost detector ordered from Beyond Belief magazine, make a late-night trip to a haunted house, despite the warnings of Malcolm's great-grandmother.

While his great-grandmother seeks her deceased husband, ten-year-old Malcolm and his best friend Dandy have no trouble finding a ghost on which to test Malcolm's latest gadget--a ghost zapper.

When Malcolm gets a school assignment to write a research report on a long-dead local hero who wrote a book about his adventure-packed life, he is shocked to meet the author's ghost, who reveals that he was a fake.

Ten-year-olds Malcolm and Dandy think their ghost-hunting days are over when they start fifth grade with the toughest teacher in their school, but Malcolm's photographs for the yearbook reveal that the school is haunted.

At the county fair, ten-year-olds Malcolm and Dandy face a real ghost in the Screaming Mansion, while at home, Malcolm's sister Cocoa's attempt to become Fair Queen has the family in turmoil.