After Timmy tells Poof a scary story, the baby's' crying keeps him up all night, so Timmy wishes for no light for twelve hours of the day. Little does Timmy know, that when his godparents are kept in the dark for longer than eight hours, they become "Scary Fairies" and turn on their godchild.
After Timmy finished reading Poof "The Super Scary Boogie Monster Who Lives Under Your Bed and Will Totally Eat You When It Gets Dark," Poof starts crying, causing a lightning storm to start in Timmy's room. Wanda scolds Timmy, and after they turn out the lights for bedtime, Poof freaks out, so Wanda asks Timmy if she can turn on Poof's nightlight. Timmy agreed since night lights are small and only show a little light. However, Poof's nightlight is so big, bright, and hot that it could burn through metal and blinded Cosmo. Timmy wishes to turn it off. Unfortunately for Timmy, morning quickly arrives and he is woken up by Cosmo after only sleeping for a measly twelve seconds. Timmy wishes for twelve hours with no light and that the only source of light would be his flashlight.
After the wish, Dimmsdale is plunged into darkness and Wanda warns Timmy that after eight hours with no light, fairies turn into scary fairies who eat their godchildren, but Timmy laughs it off and falls asleep. After ten hours, he finally wakes up in a cauldron and sees that Cosmo and Wanda are trying to eat him, so he escapes downstairs where he bumps into his parents. There, a lost Chet Ubetcha tells them that three Saber-Toothed Tigers With Night Vision escaped from the zoo. The tigers then appear and attack Mom and Dad. Timmy runs away back to his room, where Wanda tells him they are back to normal, but Timmy turns on his flashlight and sees they're still scary, so he runs out of his house and falls, and at the bottom, Dad tells him he moved his house up to a hill for the view. As they dragged their lacerated bodies to the hospital, Timmy plans to stay there until the light comes back on, only to get a call from Dad telling him that when he moved the house to the top of the hill, he also moved it closer to the freeway.
Suddenly, a bus driven by Cosmo and Wanda crashes into Timmy. After the scary fairies crash into Timmy with a train and an airplane, Timmy checks his watch to see that he has to survive ninety minutes more of darkness. After some more wandering around, Timmy finds Crocker hanging from a rope from a helicopter piloted by Mrs. Crocker. After revealing that he is wearing pork chop underpants, Crocker gets mauled by the saber-toothed tigers. After the attack, Tootie phones Timmy and tells him she is near, and she suddenly appears. Panicked, Timmy tries to run but continuously hits a brick wall and faints.
At the hospital, Timmy learns that he was unconscious for an hour, so that he has half an hour of darkness to go. Much to his disgust, he also learns that Tootie saved him by passionately giving him CPR. He escapes but keeps running into Crocker, Tootie, the tigers, his bandaged parents, and Cosmo and Wanda, who at this point have turned into hideous, bloodthirsty monsters. But when Timmy is rounded Tootie, scary Cosmo and Wanda, Crocker, his mummified parents, and the vicious tigers at the edge of the hospital's roof with ten seconds left, he screams and manages to get out of the darkness just before he got mauled by the freakish group, and everything goes back to normal.
Still screaming for his life, Timmy is suddenly in the front of his house, with Cosmo and Wanda grinning at him, entertained. At first, Timmy refuses to admit that he was scared, so Wanda poofs it back to darkness, making Timmy admit that he was scared and she put the lights back on. Cosmo then accidentally reveals that scary fairies aren't real, and Wanda tells Timmy that she made up the scary fairies to teach him to not scare Poof. Timmy apologizes to Poof and is about to go enjoy the fresh air, but falls from the hill his dad put the house on and faints, and Tootie goes to give him CPR again.