A routine trip to New York turns perilous when ex-operative Tom Keen is recruited by a mercenary chief to help rescue a kidnapped CIA agent.

The Halcyon team scrambles to rescue Scottie's close family friend after he's falsely arrested for espionage in a dangerous foreign country.

A plane crash in the Ural Mountains sends Tom and Nez to Russia on a covert operation to infiltrate a mysterious, top-secret military facility. Scottie enlists Mr. Solomon to find answers about her husband.

Tom and Mr. Solomon go under cover on an international flight that they believe will be hijacked by a ring of ruthless thieves who steal classified material. Howard urges Tom to find proof of a conspiracy orchestrated by Scottie.

When a wealthy businessman, his wife and young son are abducted by professional kidnappers, the Halcyon team is tasked to get the family back. But with time running out, the team must make a dangerous choice. Meanwhile, Tom risks exposure to save Howard from Scottie.

Tensions escalate between Scottie and Howard forcing Tom to reach out to an unexpected ally for help. As explosive family secrets come to light, Tom races against time to learn the truth about Whitehall.

In the explosive season finale, Scottie and Howard battle for control of Halcyon and the dangerous technology tied to Whitehall. Tom clashes with Mr. Solomon as he makes a fateful choice.