In the Edwardian era, in Hocombe Woods, Doris Mann, [Angela Douglas], and Albert Potter, [Jim Dale], are courting when a routine search for a peeping Tom veers into danger. Doris is abducted by a monstrous figure named Oddbod, [Tom Clegg], who leaves behind a single finger as a grisly clue. Alarmed, Albert rushes to the local police station to report what has happened, where he speaks with Detective Constable Slobotham, [Peter Butterworth], who in turn informs his superior, the henpecked Detective Sergeant Sidney Bung, [Kenneth Williams], a veteran investigator who has been tracking disappearances in the same woods.
As the investigation unfolds, the team treks deeper into the eerie heart of the forest and discovers the secluded Bide-A-Wee Rest Home. There they are ushered into a dim sitting-room by Sockett, [Bernard Bresslaw], the loyal butler. The mistress of the house, the seductive Valeria Watt, [Fenella Fielding], greets them with a knowing smile and then awakens her electrically charged brother, Dr. Orlando Watt, [Jon Pertwee]. Watt’s strange power makes him appear and vanish whenever he is plugged in, turning the strange mansion into a place where danger flickers as brightly as the neon in his circuitry.
The following day, Bung, Slobotham, and Potter question Dan Dann, a former lavatory attendant who once worked at Bide-A-Wee as a gardener. Before he can reveal anything important, Dann is silenced by Oddbod, cutting the investigation short. Meanwhile, a police scientist accidentally creates a second creature—Oddbod Junior—when Oddbod’s finger is subjected to an electrical charge. After eliminating the scientist, Oddbod Junior makes his way to the mansion, where Valeria and Watt are busy turning people into mannequins to sell them as decorative figures.
Bung arrives back at the house to investigate Dann’s death and becomes infatuated with Valeria, losing sight of the danger that surrounds him. Potter discovers Doris—now in mannequin form—inside a milliner’s shop, but there is no conclusive proof that the woman in the shop is truly Doris. Bung returns to the house and finds evidence linking Valeria and Watt to the mannequin, yet remains oblivious to the broader plot. Desperate, Valeria and Watt use a potion to transform Bung into a hairy monster and command him to steal the mannequin they desire.
With the trap set, Bung and Slobotham orchestrate a sting in Hocombe Woods, with Slobotham disguising himself as a woman to act as bait. Emily Bung, Bung’s sharp-tongued wife, follows, convinced that her husband is having an affair, and she is quickly captured by Oddbod Junior, while Slobotham falls to Oddbod. Bung, now teamed with Potter, tracks the footprints back to the house.
A brutal confrontation ensues as the Oddbods are finally forced to retreat from Bung and Potter, who are aided by Slobotham. Doris is brought back to a human form, though Emily has been left as a mannequin. A heated battle erupts, and Albert, in his monstrous form, defeats the Oddbods. Dr. Watt menaces them with a petrifying liquid, but the situation worsens when Rubbatiti, the mummy brought back to life by a lightning strike, reanimates and menaces Watt. The two fall into a boiling vat in the cellar, killing them both.
In the aftermath, Albert and Doris marry and begin their life together. Bung, whose home still lacks electricity, cannot reverse his wife’s transformation, and he remains living with Valeria, who has become a kind of unintentional companion in his electric-free world.
