Before returning home from New York, Rand Peltzer buys for his son a cute furry pet known as a Mogwai. The shop's owner warns him that 3 rules must be followed when caring for the creature: Keep it away from bright light, don't get any water on it, and never ever feed it after midnight. Rand takes it home, and his gift is an instant hit: Billy loves his adorable new pet, names it Gizmo and takes it everywhere he goes.

Unfortunately, he and his friends also begin breaking the rules of Mogwai care....