Naughty @ 40 is a comedy-drama that revolves around a simpleton Harvinder ‘Happy’ (Govinda). Happy, a 40-year-old man, who lives with his parents in London. He wishes to get married, however, due to his sleep-walking problem women reject him all the time. He finally marries a girl named Gauri (Yuvika Chaudhary). Gauri is much younger than him and is childlike, which frustrates Happy. He then gets sexually involved with a London-based model. Happy ends up in trouble when Gauri finds out about the act.