Tuppence and Tommy Beresford are agents for the British Secret Service.
Agatha Christie tried her hand at numerous genres, all connected to mysteries, especially in her early years. One of these experiments introduced two young people reunited after several years, both in need of money. While joking over a lunch about becoming 'adventurers' for hire, they are overheard by the head of the British Secret Service. He saw in them just the pair he needed to handle a delicate mission. Thus did Tommy and Prudence, nicknamed Tuppence, get their introduction into both espionage work and solving murders.
A few years later, Dame Agatha collected more tales of this delightful pair of snoops into another volume but after that, they fairly retired for they were not heard again until 12 years later with an adventure fighting German spies at the beginning of the Second World War. Afterwards, they disappeared as Miss Marple and Hercule Poirot took center stage.
Perhaps it was nostalgia that caused her to resurrect her two lovebirds 27 years later. She had aged them properly for they were now in the late sixties but they were just as adventurous as they had been when penniless years before.
One part of me did not feel they belonged in this collection. The two adventures they had during the post-War period were really murder mysteries. Still, numerous lists of spy series I have seen have included the Beresford's and, since I have been reading Agatha Christie stories since I was little, it was fun to revisit her.