The Drifter by Nicholas Petrie

Marine veteran Peter Ash finds himself in Milwaukee repairing a porch for the widow of one of his closest friends from his two tours of duty, Jimmy, who recently committed suicide. Repairing the porch is no easy task with a huge, smelly, and aggressive dog trapped underneath, but Peter finds that the animal is not the biggest problem--he finds a suitcase with almost half a million dollars and plastic explosives inside. Complicating matters even more, Peter is suffering from PTSD and finds it overwhelming to be inside. After notifying Jimmy's widow, Dinah, of his discovery, Peter decides to delve into the issue of where the suitcase came from.  Peter's search leads him to uncover what Jimmy was doing before his death and allows him to form a companionship with the aforementioned dog, Mingus.  The Drifter is a great debut thriller full of action and memorable characters.  A fabulous read-alike for Lee Child, Thomas Perry, and Owen Laukkanen's Kill Fee.