It is 1943 in London at the height of the German blitz. On the eve of his marriage, the Earl of Harpenden puts up a drunken American Lieutenant for the night; and in the morning fixes him up with a former girlfriend. The American mistakes the Earl's fiancee for the girlfriend. Add a Fench officer , the fiancee's father (a deadbeat Duke), and the amorous girlfriend and you have a situation where mistaken identities lead to comic chaos.