Now married and bored with quiet domesticity, Tommy and Tuppence Beresford accept a proposition from their old intelligence handler, Mr Carter: take over Blunt's International Detective Agency, a recently broken-up spy front whose proprietor has been arrested, and run it under cover while watching for enemy messages. With their assistant Albert installed in the outer office, the couple wait for espionage work that rarely comes, and in the meantime take on the ordinary clients who walk through the door, treating each case as a game. The conceit that links the stories is literary pastiche: in every assignment Tommy and Tuppence deliberately adopt the methods, mannerisms, and patter of a famous fictional detective of the era, and often the detective's chronicling sidekick as well. They reason like Sherlock Holmes and Dr Watson, like R. Austin Freeman's Dr Thorndyke, like G. K. Chesterton's Father Brown, like Baroness Orczy's Old Man in the Corner, and at one point like Christie's own Hercule Poirot. The mysteries themselves are compact and varied, ranging across a missing pearl, a vanishing woman, cryptic newspaper personals, a poisoned household, and a stabbing on a golf course. A connecting espionage thread involving a dangerous adversary tightens toward the end, when an old enemy resurfaces and Tuppence's circumstances change. Affectionate parody, light comedy, and brisk puzzle-solving run side by side throughout, making the collection as much a tribute to Golden Age detective fiction as a set of cases.