Status Updates From Tajemniczy przeciwnik

Their first meeting for making money is blown when Tuppence gives her name as Jane Finn.

Tuppence's second meeting is to search for the real Ms Finn (maybe survived) and find the Secret Treaty (government failure) she possibly was given when the ship was sinking.

Mr Carter hires them but beware of agent "Mr Brown"

Starts out with the sinking of ocean liner Lusitania.
Tommy and Tuppence are childhood friends. Tommy was in the war and Tuppence volunteered. Now they meet up and Tuppence devises a plan to make money doing anything.