Mysterious opponent

Tommy Beresford and Tuppence Cowley are a sweet couple. But there is one problem: they have no money, no job, and are always broke. So they come up with the idea to start their own business, 'Young Adventurers Ltd.', as they are best at deceiving people. And here comes the first order from a certain Mr. Whittington. The payment is excellent, but the case is so strange that Tuppence decides not to reveal her real name and introduces herself with a name she overheard in a conversation between Whittington and another person. Suddenly, the client changes his mind, hastily leaves, for some reason gives Tuppence a large sum of money, and soon disappears from the adventurers' horizon. Intrigued, Beresford and Cowley want to find out who this Whittington is and why he is so afraid of the name Jane Finn...