6Tommy and Tuppence Beresford are the protagonists of a series of novels and short stories by Agatha Christie, and mark the few ventures that Christie made into espionage tales rather than the whodunits she's known for. 'The Secret Adversary' introduces Tommy and Tuppence who feature in three other Christie novels and one collection of short stories; the five Tommy and Tuppence books span Agatha Christie's writing career. Thomas Beresford and Prudence "Tuppence" Cowley started out as friends in post-World War I Britain. Jobless and penniless, they place an ad in the paper marketing themselves as adventurers, leading to an encounter that starts their career as spies for an unnamed British intelligence agency.