Lupin sneaks into an old castle to steal a collection of priceless angel paintings; what he finds instead is a teenage girl named Flora. Despite his numerous objections, Lupin cannot seem to get rid of her, and she accompanies him back to his hideout. As it turns out, Flora is the daughter of the late Malcolm Hurst, owner of the angel collection. If Lupin agrees to let her be a thief for the next three days, she will reveal the location of the paintings. Lupin has no choice but to put up with this energetic girl all while avoiding attacks from Hurst's greedy ex-wife, who wants the paintings for herself.