Will suffers a shocking tragedy. While he considers leaving his job at API, he begins to uncover clues that point to a sinister conspiracy. Katherine questions her billionaire husband's unexpected suicide.

Will faces his first day as the boss to his former teammates. While struggling to maintain authority, he pieces together messages left for him by David. Katherine learns Tom had a secret life.

Katherine and Wheeler share their grief and confusion over Tom's suicide and find themselves closer than expected. Maggie's ex-husband returns asking forgiveness. David's son visits Will, leaving him with yet another clue to David's death.

At API, Will keeps a careful eye on Tanya. Plus, after meeting with her financial advisor, Katherine inquires about an investment her husband left her two days before his death.

Kale invites Will over for dinner and gives him some interesting information. Katherine discovers a commonality between her husband and the subject of an old obituary she found.

A security lockdown is imposed on API by the FBI and everyone must undergo a polygraph test. Will sees something of interest in Spangler's office.

The CIA asks Miles and Tanya to oversee an interrogation. Katherine receives a mysterious envelope with a picture and a drawing of a four-leaf clover. And Will makes some new discoveries.

Will and Katherine meet secretly. Meanwhile, the API team continues trying to track down Kateb, and Will discovers he shared a common interest with his late boss, David Hadas.

Will and Katherine meet secretly. Meanwhile, the API team continues trying to track down Kateb, and Will discovers he shared a common interest with his late boss, David Hadas.

The API team is forced to work with the FBI to try and locate the man they think is Kateb. Will may be able to figure out the next target destination ... but will it be too late?

In the gripping season finale, the API team tries to find their footing in the aftermath of the explosion in Galveston Bay. Plus, Will confronts Spangler.