Secret Lives Mysteries, book 1: Secret LivesMark de Castrique2022

At seventy-five-years-old, Ethel Fiona Crestwater is used to being underestimated. She looks like someone's grandma, although she's never married or had children; petite and a bit frail, she's not a threat to anyone. Or is she...?

Ethel runs a boarding house for government agents, and when someone murders one of her boarders, she springs into action—much to the surprise of her distant cousin Jesse, who has recently come to stay with her while he attends university. As he watches her photograph the crime scene, conceal evidence, and speed-dial the Secret Service Director, Jesse realizes that there's much more to Ethel than appearances suggest.

But when Jesse is assaulted and the gym bag full of cash Ethel had hidden is stolen from the basement, the pair decides it's time to launch their own unofficial investigation. With no one to trust but each other, these double-first-cousins-twice-removed form an unlikely bond and learn that the only thing truly worth risking your life for is family.