In Ukraine, Malotru arrives at the exchange location to get Marina. But on the way back, their convoy deviates from the route initially agreed upon by the DGSE, forcing him to warn Sisteron. Back in Paris, Marie-Jeanne quickly understands that Malotru’s life is at stake and confronts JJA and Ponte. Meanwhile, Jonas interrogates Iode 3 to try and prevent an impending terrorist attack in France.

Sisteron warns Marina that her cover has been blown, but that her arrest could help on another crucial assignment. Meanwhile, Malotru parts ways with Samara and comes back to France, where he is to be held in solitary confinement. Back in Syria, Jonas has lost Iode 3’s track and must turn to artificial intelligence to try and find him.

Debailly asks DGSE to help Nadia, but is refused. He attracts the CIA by approaching the Syrians, purporting to represent the Americans, and takes time off to meet the CIA (revealed as the flashforwards shown from Episode Two). Dr Balmes suggests his motivation is not love for Nadia, but craving for the double life he experienced undercover. He agrees to return to the DGSE as a CIA double agent. Meanwhile, Marina disappears in Tbilisi en route to Iran, kidnapped by the Georgian secret service to see from where she seeks help. Cyclone is rescued in an ambush near the border with Mali.

Chased by the DGSE and the CIA all the way to Moscow, Malotru tries to negotiate his return to France. The DGSE’s new head of Internal Security, JJA, initiates a full-spectrum audit of The Bureau and its new chief Marie-Jeanne, with the clear-cut intention of severing a few heads in the process.

Dumped by the DGSE, Malotru comes out of hiding and is quickly located by the Russian secret services. At the DGSE, Liz manipulates Sisteron to cause distrust between he and Marie-Jeanne. Meanwhile, Jonas begins to suspect that his mission might be hiding an ulterior motive: to ultimately eliminate the Jihadists he has been targeting.

Arrested for Espionage by the Russian secret services, Malotru is tossed aside and left to the mercy of other inmates. Back in France, the DGSE is striving to understand his motives before making a move. Marina’s phone has been hacked and used in a cyberattack against the Boulgakov Centre. Back in Iraq, Jonas suspects that a seemingly repentant Jihadist may be playing him to sneak his way back to France.

Karlov asks Malotru to join the FSB in Moscow. In Paris, Sisteron and the entire Bureau must answer to an inquiry questionnaire on Marie-Jeanne, which JJA intends to use against her during the next board meeting. Meanwhile, Marina is resenting the way the Bureau is using Micha, afraid to once again leave a trail of destruction in her wake.

Debailly continues to investigate the leads on Cyclone. Nadim traces Debailly's daughter Prune and starts asking about him. Marina and another agent force a colleague at the Institute to refuse the secondment to Iran. Debailly realises that the Syrians and Russians are tailing him, and finally tells Duflot about Nadia and her involvement with the Syria talks. Meanwhile, the DGSE identifies who is holding Cyclone for ransom in Algeria.

Nadia refuses to betray her country, and is angry at Lefevbre's revelations. Ill from the stress of her situation, she confesses to Nadim, and is flown back to Syria. The Russian FSB confronts DGSE and buys its silence. In Algeria, DGSE fails to plant a bug on the General holding Cyclone; Cyclone is handed over to ISIS. Marina is trained to deal with interrogation by Marie-Jeanne, tested by an Iranian agent pretending to be Reza's wife, and offered the Iran secondment. In flashforward, Debailly continues to talk to the CIA; the Americans do not fully believe his story.

ISIS threatens to execute Cyclone; Debailly is asked to work on his rescue. Nadim tries to blackmail him with Nadia's life, wanting him to betray Syrian sources; Debailly refuses to do so. The Americans pull out of the Sahara operation; DGSE suspects they may have a mole. Marina is further tested before leaving for Iran. Debailly shares details of the rescue plan for Cyclone with his colleagues.

While under intense pressure from the FSB to cooperate, Malotru is considering how to approach a cyber operations officer. Back in France, Marie-Jeanne seeks Mag’s advice, only to find out that JJA had coerced him to resign and that she could very well be next. Jonas hires an expert to infiltrate an Islamist financial network.

Just as Karlov is beginning to lose patience, Malotru suggests recruiting Ellenstein. Back at the DGSE, Marie-Jeanne is monitoring a cyberattack, hoping to track down the person responsible for hacking Marina’s phone. Meanwhile in Mosul, Jonas and Jean-Paul are searching for a way through the ravaged city to get to the Collector.

Under Karlov’s watchful gaze, Malotru initiates Ellenstein’s recruitment. At the DGSE, Sisteron suspects that Cesar is not ready to go on a mission and will not be able to hold his legend undercover. Back in Raqqa, still under Daesh’s occupation, Jonas and Jean-Paul join a battalion of Yazidi women to track down Iode 3.

Mikhaïl Karlov receives a parcel with the USB key which Sylvain uses at work. Both surprised and worried, he tries to reach the young hacker and learns that the young man is on a mission in Seoul. Meanwhile, Alexis Bakatine, the head of security at the FSB, is continuing his investigation into the spy "Black September" in order to find out if Pavel is a double agent.

Debailly continues to be tailed by the Russians. The DGSE meet an Algerian with information about Cyclone. They decide to recruit Nadia; Marie-Jeanne realises that Debailly has not told her the full truth, and confronts him. She also helps Marina compel a second colleague to refuse the Iran secondment, and teaches Marina a lesson about not getting close to her contacts. Debailly continues to be interrogated by the CIA in flashforward; it is revealed that Dr Balmes works for the Americans.

Marina begins to socialise with young Iranians, including Zamani, the son of a well-connected minister. She finds adapting to the internal politics a challenge. The Americans fail to rescue Nadia in an ambush in Lebanon. Debailly threatens to withdraw co-operation; the CIA retaliates by threatening to betray him, then asks him to make a better offer. Debailly offers to share a prospective DGSE source within Iran's nuclear industry. The DGSE discovers that one of the IS executioners, Boumaza, is a French national.

In Moscow, Malotru welcomes César, who has taken Ellenstein’s identity. Back in Damascus, the Syrian authorities refuse to let either Jonas or Jean-Paul access the morgue, where Iode 3’s body most likely lies.

The episode starts with a flashforward of Debailly continuing to explain his story. Nadim investigates Paul Lefevbre, and tells Nadia not to see him again. But he finds them having dinner, and interrogates Lefevbre. Nadia confesses her true reason for being in Paris, and Debailly realises that their relationship puts her in danger. Meanwhile, Reza starts to flirt with Marina, and she has to rebuff his advances. DGSE tries to find out if the Algerians are holding Cyclone, and must stop his mother travelling there to search for him.

DGSE makes contact with Algerians holding Cyclone, and Sisteron goes to Algeria. The Syrians continue to investigate Paul Lefevbre, testing him by mugging him in the street. They also seek help from the Russians. Meanwhile, DGSE puts Marina through a surprise mock interrogation. DGSE is also concerned that Cyclone's capture could have compromised the Sahara Desert operation, in which the Americans are involved. In flashforward, Debailly continues to recount his story to the Americans.

Debailly recalls when he first met Nadia, and continues to agonise about her fate. The CIA confirms its interest in Zamani, but Debailly and Marie-Jeanne fall out over Marina's mission; Debailly persuades Deflot to replace her with him as Marina's handler. Debailly tells Marina to get close to Zamani. The Iranian secret police take an interest in Zamani and Marina. The French Government authorises action against Boumaza; Cyclone cultivates the jihadist's family, and Sisteron poses as a supportive lawyer. Duflot continues to hunt for the mole inside the Bureau. Nadia is held prisoner in Syria.

The DGSE recruits the jihadist's sister, planning to trap and kill Boumaza. Meanwhile the Iranian secret police continues to investigate Marina, and DGSE discovers this from a source. Marina is recalled to Paris, but leaves on an expedition before receiving the message, and is arrested. In Syria, Judge Badran interrogates Nadia about her affair. Duflot suspects that Dr Balmes, who has resigned from the DGSE, may have been the CIA mole, but fails to find any evidence.

DGSE receives a report that Nadia has been executed in Syria, but the CIA has warned Debailly to anticipate false reports, and agrees to work with him in return for his Iranian source. Marina is interrogated by the Pasdaran, then released, and she returns to Paris. Duflot tells Marina not to contact Zamani, who is coming to Paris, but Debailly then tells her to contact him again. Sisteron and the sister arrange to meet Boumaza on the Syrian border, where the Turkish military intend his capture. However, the sister is communicating secretly with her brother. Meanwhile, after a mock execution, Nadia is given her 'freedom', but forced to work undercover for the Syrian government representing its rebels abroad.

Duflot discovers that Debailly disregarded his order to Marina not to contact Zamani, dismisses him for misconduct, and reinstates Marie-Jeanne as handler. But Duflot's boss decides Marina should continue cultivating Zamani. Debailly maintains contact with the CIA. Nadia, visiting France, refuses to see him. Meanwhile, Sisteron sets out with Boumaza's sister to meet the jihadist. Turkish special forces extract Sisteron, but they are ambushed by jihadists and Sisteron is captured. Too late, DGSE discovers the sister's communication with Boumaza.

Boumaza takes Sisteron into Syria. DGSE decides not to attack, to protect its local agents. He hears that Turkish forces have his sister, and exchanges Sisteron for her, after cutting off his foot. DGSE ask Debailly back unofficially to lead a team to hunt Boumaza; he plans assassination using a suicide bomber. Duflot notices, from the GPS history of Debailly's phone, the weekend when it was untraceable (when he was with the CIA). He plants a bug in Dr Balmes's office. Nadia, in Paris, is reluctant to continue her role, but Nadim forces her; she contacts the DGSE for help. Celine arranges for Nadia to meet Debailly. Meanwhile, Marina returns to Iran, tasked with recruiting Zamani. Debailly passes her reports onto the CIA.

Continuing her meeting with Debailly, Nadia insists that DGSE help her escape from her forced role as figurehead for the Syrian rebels. Debailly decides to compromise Nadim by forging his application for asylum; he defects, and Nadia is taken away to a safe house. Debailly and Dr Balmes discover the bug in her office. The CIA stands Dr Balmes down from its service. Meanwhile, the French are close to securing Zamani as a source, only to find he has just been recruited by the CIA. Debailly continues to plan to execute the jihadist.