Mason Kane and Nadia Sinh – top agents of the independent spy organization Citadel – collide with a nefarious, new syndicate – Manticore – leading to catastrophe. Eight years later, Mason Kane is living a quiet life as "Kyle Conroy," with no memory of his past. Until one day an old colleague enlists his help to stop a now powerful Manticore from creating a new world order.

After the shocking revelation of Abby’s former identity, we learn of the past entanglements between Mason, Nadia and Celeste, and a horrific decision that reverberates still today. Meanwhile, Nadia and Kyle land at the Manticore compound in Morocco and risk their lives to free their fellow spy. But their hero’s welcome is short-lived as they are forced to grapple with a dangerous accusation.

Nadia, Kyle and Carter are forced to work together to escape from Manticore and protect the X Case, but suspicion of one of our heroes reaches a boiling point, leading to an explosive reckoning.