Undercover operative Tom Keen joins forces with Susan "Scottie" Hargrave, the brilliant and cunning chief of Grey Matters, a covert mercenary organization that solves problems governments don’t dare touch. While on the hunt for Liz’s attacker, Tom secretly discovered that Scottie is actually his biological mother. Now, as they team up to employ their unique skills and resources in a dangerous world of deadly criminals, Tom begins his own covert mission to find out more about his shadowy past.
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.
When an American journalist and close family friend of Scottie is falsely arrested for espionage in a dangerous foreign country, the Halcyon team mounts a last-ditch effort to rescue him before time runs out.
After a plane crashes in the Ural Mountains, Tom and Nez go undercover in Russia to infiltrate a mysterious, top-secret military facility. Meanwhile, Scottie enlists Mr. Solomon to find answers about her husband.
When ruthless terrorists escape from a “black site” prison in Manhattan, Tom and the Halycon team must lock down the city and find the terrorists before disaster strikes.
Tom and Mr. Solomon go undercover 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.