The task force moves to a new HQ under the assumption that their last offices have been compromised. Their top priority is finding Alex, the prime suspect in Michelle's murder, a traitor and a fugitive. They know Alex had help escaping his hotel room, but they don't know it was Faber who helped them.  Faber meets with the Rezident and warns him the O'Connors knew he was dirty before they even knew his name. The Rezident responds that if the FBI finds anything on him, Moscow will no longer have any use for him, so Faber heads to the O'Connor home to remove whatever evidence the family found on him.  Up in Canada, Natalie is out for a run when she spots a suspicious man. She races back to the house, grabs a gun from the barbeque stash and takes the gunman out. She then runs inside to warn Victor, who is in the shower and has no idea they've been found. As Victor comes outside he sees Natalie snap the neck of the other assailant. Suddenly Natalie gets a message - Alex is hurt. They have to go back to the lion's den. So much for their new life...  Meanwhile, Mark and Katya, with a semi-conscious Alex bleeding out in the backseat, race to Sarah's school to pick her up before the SVR takes her out. When she gets out of singing practice, Sarah gets a call from Mark telling her she's in grave danger. As she makes her way out of the building she comes across a janitor... but he's not a janitor, he's an SVR operative. He grabs her and puts a knife to her throat, but just as he's about to kill her, Mark comes up behind him and stabs him repeatedly as a terrified Sarah looks on. Mark and Katya now have the difficult task of explaining to Sarah who they are and the dangerous secrets they've been keeping from her. Despite knowing the risks, Mark decides to sneak back to the house to retrieve his laptop with the evidence against Faber and Christoph. He makes it there undetected but it's too late - Faber beat him to it. Now the O'Connors have nothing to show the FBI.  But Alex has a plan: he decides to contact Sam to let him know about Faber and hopefully convince him to let him look at Christoph's top-secret files. If Alex can find a pattern in his operational tactics, maybe they can predict where Black Dagger will strike. Victor points out that Sam will never believe a fugitive, but Alex is determined to make him. He intercepts Sam on his morning run and tells him he didn't kill Michelle. Surprisingly, Sam believes him and agrees that someone must have set him up. Alex is taken aback, and Sam uses the opportunity to punch Alex in the gut. Alex pulls a gun on him and tells him about Faber and Oscar Christoph. Sam doesn't believe him, but Alex provides details that make it impossible for him to ignore.  Sam heads to the office to double-check Alex's evidence and realizes Alex was right - Faber is the mole. He sneaks off to meet Alex, and just as he suspected, Faber follows him. In a deserted alley, Faber apologizes and then pulls a gun on his old friend, while Sam tries to get him to turn himself in. Faber refuses and shoots Sam, only to be shot in the back by Alex, who's been watching the whole scene. As Faber lies dying, Sam slowly gets up, grateful to be wearing a bulletproof vest. Alex is relieved - now everyone will know he's innocent! But Sam warns him that the way the task force will see this is, Sam stole classified files to turn over to a Russian agent, and when a federal agent caught them in the act, Alex killed him. Sam tells a devastated Alex to take the files and go find them something they can use on Christoph.  Back at the hotel, Alex and Katya pour over Sam's files. Suddenly Alex finds the triggerman's pattern: Christoph makes his attacks look like accidents. He's been spotted near dozens of catastrophes over the years at water treatment facilities, coalmines and power stations. All of these explosions, which used existing materials as fuel sources, shifted geopolitical power in one direction or another. There are still a ton of potential targets, but the O'Connors are finally getting somewhere!  Oscar Christoph attends an energy summit in Berlin, Germany, where he has a "meet-cute" with Elizabeth Simpson, one of the conference's speakers and a high-ranking member of the U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration. Oscar poses as Marcos, a South American energy journalist determined to save the world. The two begin a long-distance relationship, meeting up every few weeks whenever they cross paths at various conferences.  In the present day, Oscar cooks dinner for Elizabeth at her apartment in New York City, and they discuss their relationship. Elizabeth wants more and fears he's secretly married because they meet up so infrequently and she's never met his family or friends. He reassures her, but when she falls asleep, he hacks into her computer and copies top-secret files detailing valve conversions at East Coast gas facilities. When Elizabeth wakes up, Oscar tells her he has to go to a meeting in Boston, but he really goes to his workshop, where the Rezident calls him. Black Dagger will occur in two days. The Rezident wants him to take care of Elizabeth, whom he considers a loose end.  "Touch her, I kill you," Oscar responds.
Hunted by both the SVR and the FBI, the O'Connors go on the run, desperate to out Faber as the mole before it's too late.