N or M?

In World War II, the RAF fights to defend against the Luftwaffe, but Britain also faces a hidden danger - Nazis masquerading as normal citizens. To combat this threat, the Intelligence service turns to unlikely spies, Tommy and Tuppence Beresford. Their task: to identify a man and woman among the colorful guests at the Sans Souci seaside hotel. But this is far from a leisurely stroll, as N and M have already eliminated Britain's top agent. Agatha Christie's 'Marple' was a bestselling novel in the Sunday Times for the week of 12-09-2022.