A Good Man Gone by A.W. Hartoin

Mercy Watts wants exactly one thing: two weeks without a case. Naturally, someone dies.
Her parents are on a cruise, the family detective agency is supposed to be somebody else’s problem, and Mercy fully intends to enjoy being a nurse with absolutely no interest in investigating anything.
Then longtime family friend Gavin drops dead of an apparent heart attack.
Mercy’s father, Tommy Watts, gets one of his famous feelings from somewhere in the middle of the Atlantic and asks her to look into it.
Just a few questions, he says.
A few questions turn into an old murder. A bride killed on her wedding day. Two deaths with no obvious connection—and one very inconvenient possibility that someone has gotten away with murder.
Mercy may not want to be a detective, but being a Watts means trouble has a way of finding her anyway.