It's 1910, and Raoul is a Parisian delivery man by day and scientist by night who is determined to brainstorm an important new invention. With the help of his friend Emile, a cinema projectionist with women on the brain, Raoul attempts an experiment in a greenhouse that has an unexpected side effect -- a tiny flea has suddenly expanded until it's seven feet tall. The enormous flea gets loose and it's not long before word is out that a monstrous bug is haunting Paris. However, while mean-spirited politician Victor tries to snare some publicity by making people afraid of the bug before he catches it, Lucille, a pretty nightclub performer, makes a surprising discovery -- the big flea is not only gentle and friendly, he's a gifted guitar player, and decked out in a suit and a hat, he's soon impressing patrons as part of her act.