This was Nix and Dawson story. We were introduced to Nix in the last book. He’s Brennans best friend and coworker. They started dancing around each other while Dawson works on the construction site. Dawson is the child of an alcoholic and had never felt like he mattered or cared for. This upbringing affects his adult life in the form of his heavy drinking.
Nix is a recovering user and sees the signs. He’s literally taken by Dawson that he bails him out of a jam. When that problem occurs again, he suffers the consequences of Dawson actions.
These two together shouldn’t work but they do. It was heartwarming to watch them repair the broken parts to be together.