Old Guns by Alan Lee

Everyone knows Mackenzie August doesn’t take on trainees. The work is personal and often dangerous. But when Edgar Betts comes knocking, Mackenzie is forced to reconsider.

Mackenzie owes Edgar, and Edgar’s pleads with him, father to father. His son Elijah lost his PI license, which he never should have received in the first place. Elijah plans to get the license back and continue his career, but he’s a young gun too foolish to survive. Please, the father begs, help my boy. Teach him, train him.
Little do either of the men know, Elijah is already in trouble, far worse than they could imagine.