As command of the operation shifts out his hands, Bosko shares a grim reality; Naomi receives troubling news out of Iran; Richardson runs a rogue operation; Felix gets overtaken by events; Martian, desperate, makes a devil's bargain.

Martian buys time with a bluff to Langley. Danny crosses the Rubicon.

Martian's approach doesn't go to plan. Sami makes a startling confession.

Mr. Dalaga puts a lot of pressure on Sami; Bosko is briefed on how big of a scale Valhalla is; Jerome is warned that he should listen to his horoscope; Martian must force his hand when Poppy is threatened; Henry strategizes a high-risk recruitment.

Martian scrambles to unravel Cossack's game. Osman plays his hand.

Feeling the heat from Langley, Henry sends Owen to hunt for clues in Minsk. Danny's work with Reza generates an unexpected outcome. Sami is confronted by Osman about sensitive issues. Martian, seeing the size of the stakes, sets a rat trap.

Henry and Martian wade into a diplomatic incident with the Belarusian delegation; dropped into her mission by Naomi, Danny walks a tightrope. Poppy and Martian attempt a fresh start. Osman threatens Sami.

Henry questions Martian's thinking. Bosko is briefed by Langley on a top-secret operation. Poppy makes a startling discovery. Martian confronts Sami about why she's in London and finds a needle in a haystack, before a heated session with Dr. Blake.

Dr. Blake arrives from Langley and is put to a test by Martian and Henry. A spooked source threatens to put an operation at risk. Danny's cover is put in play. Martian, overtaken by events, begins to question Sami's motives.

Covert CIA agent Martian is called back to London Station. An incident in Belarus puts Bosko and Henry on a collision course with Langley. Danny learns a lesson. Someone unexpectedly reappears in Martian's life. Series premiere.