At a hospital in New York, Alex, a police officer, meets Leo, a boy who has the ability to get out of his body and pass through the walls like a ghost. Both team up with Mary, an intrepid journalist, to capture a disfigured villain who terrorizes the city.

Paris, 1910. Emile, a shy movie projectionist, and Raoul, a colourful inventor, find themselves embarked on the hunt for a monster terrorizing citizens. They join forces with Lucille, the big-hearted star of the Bird of Paradise cabaret, an eccentric scientist and his irascible monkey to save the monster, who turns out to be an oversized but harmless flea, from the city's ruthlessly ambitious police chief.

An orphan boy named Tim is afraid of the dark. However, when the stars start going out in the sky, he finds himself exploring the world of the night, alongside his new friend, the Cat Shepherd.