'N or M' by Agatha Christie, Chapters 06 to 11

Chapter 6:
Tommy and Tuppence Beresford, disguised as Mr. Meadowes and Mrs. Blenkensop, continue their investigation at the Sans Souci guesthouse. Suspicion mounts as they observe the peculiar behavior of their fellow guests. Tommy's conversations with Carl von Deinim reveal the latter's wartime struggles, hinting at a potential hidden agenda. Meanwhile, Tuppence senses unease among the guests and grows closer to deciphering the mysterious identities of "N" and "M," suspected enemy spies.
Chapter 7-8:
Tuppence cleverly investigates the other residents. A tense moment arises when a guest attempts to warn her about danger. Tommy secretly receives information from the government that "N" might be closer than they think. The Beresfords work together to test the guests' reactions to subtle provocations, inching toward the truth.
Chapter 9-10:
The atmosphere grows tense as Tuppence uncovers a concealed document that could link one of the guests to espionage. Tommy follows a lead outside the guesthouse, leading to a perilous encounter. Tuppence continues to play her role brilliantly, gathering critical clues about the identities of "N" and "M." A shocking twist reveals the involvement of a guest previously deemed innocent.
Chapter 11:
The tension peaks when an unexpected ally provides the Beresfords with crucial evidence. They piece together a web of deceit and uncover the larger espionage plot. The real danger of "N" and "M" becomes more apparent as Tommy and Tuppence prepare for a final confrontation to expose the enemy.