Her eccentric and childless guardian, Mr. Penicuik, is leaving Kitty all of his vast fortune - but with one condition. She must marry one of his five grand-nephews.

However, Kitty's clear favourite - the rakish Jack Westruther - doesn't appear at all interested in the arrangement. To make Jack jealous, Kitty impulsively convinces his cousin, the kind-hearted and chivalrous Freddy Standen, to enter into a pretend engagement.