The hunt for a suspected terrorist takes an emotional toll on Kyle who is convinced that he encountered the suspect during his service in Afghanistan.
Frank Rourke heads LAPD's Special Investigation Section (SIS), a unit that goes after the worst of the worst. There's just one problem: Frank is almost as corrupt as those he chases. His behavior hasn't gone unnoticed however, and the untainted Kyle Craig is brought in to serve as the upper LAPD brass' eyes and ears on Rourke by becoming the elder detective's trainee.
Also on the team is Detective Rebecca Lee, who was rescued from human traffickers by Frank when she was 4 years old and looks up to him as the father she never had. Tommy Campbell is a former pro surfer who's usually seen in board shorts; he may still look like a surfer, but he's traded in riding the waves for the dangerous highs that come from swimming with a different type of shark.
Alyse Arrendondo is Kyle's smart and cynical wife who's a history teacher who loves and greatly admires her husband and his insatiable drive - despite his reckless displays of heroism. Holly McCabe is an unapologetic Hollywood madam who looks like a woman half her age and takes pride in how well she treats her girls. In addition to having a tacit understanding with Frank, they are also a couple.