In the novel Dead Man's Folly, Sergeant Frank Cottrell is the one of the police officers investigating the murders at Nasse House.

Sergeant Cottrell is described as "a brisk young man with a good opinion of himself, who always managed to annoy his superior officer." One of his roles during the investigation was apparently supervising the search of the grounds for the missing Hattie Stubbs. Part of the way through the search he was able to report that he was sure Lady Stubbs could not have passed through the main gate. The second gardener was there collecting admission fees and would swear she did not go through it. Cottrell also supervised matters such as removing the body of Marlene Tucker and questioned minor witnesses such as Ladt Stubb's maid to ascertain what she was wearing.

The text records that "Inspector Bland much preferred the rural wisdom of (constable) Hoskins to the smart know-all attitude of Frank Cottrell."

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