Dr. Paul Carruthers, the kindly doctor of Heathville village, is convinced that Henry Morton and Martin Heath, the cosmetics manufacturers for whom he works, have become rich through formulas that he has developed. Driven mad by the desire for revenge, the doctor creates a strain of giant killer bats that attack when they smell a special scent he has formulated. Carruthers' first victim is Heath's son Roy, who volunteers to test the doctor's new aftershave. When Roy's dead body is found bearing strange wounds, newspaper reporter Johnny Layton and photographer One Shot Maguire come to Heathville to investigate. As a giant bat attacks Tommy, Heath's other son, Johnny catches sight of the creature, but no one will believe his story. After Morton's son Don dies of the same mysterious wounds, Johnny finds a bottle of aftershave in his bathroom and, recognizing the scent from the other victims, begins to suspect Carruthers. To eliminate the suspicious Johnny, Carruthers gives him a bottle of aftershave, which One Shot uses. As the bat swoops down out of the night sky, Johnny kills it, but the doctor creates another "devil" bat. Carruthers visits his next victim, Henry Morton, and hints that he is responsible for the murders, but before Morton can inform the police, he falls victim to the bat. Next on Carruthers' list is Heath's daughter Mary, but when the bat fails to gain entrance to her room, Johnny sneaks into the doctor's lab and finds the creature. After spilling the fatal scent on the doctor, Johnny forces him at gunpoint to await the bat's arrival. As the creature appears, Carruthers struggles with Johnny and runs into the night, only to become a victim of his own creation. After killing the doctor, the bat swoops after Mary, but the sheriff shoots the creature before it can harm her.