प्लॉट

Philip and Elizabeth must stop an assassin from taking out key US scientists, while Stan and the FBI hunt the same man. Grannie shocks Elizabeth with the truth of what happened between Philip and Irina in a New York.

The KGB hired a hit-man to murder US scientist involved in the missile defense shield program but changed its mind, fearing the backlash. Philip and Elisabeth must find and stop him, without details. They track him down, but can't prevent a bomb taking out a scientist and an FBI agent on guard, so grim retaliation is sworn. Both sides profit from pillow talk, as new resident Arkady has inherited the undetected mole, but Elisabeth's jealousy over Philip's relationship with the mother of his son undermines their 'front' marriage, which is now only kept together by parenting.—KGF Vissers

Previously on 'The Americans': Phillip wooed Martha, his FBI contact. Agent Beeman had sex with Nina, his Rezidentura mole, and wants to get her exfiltrated. Agent Gaad says he'll "think about it." Phillip, meanwhile, reconnected and had sex with Irina, his girlfriend back in Russia before he became a spy, but told Elizabeth that nothing happened.

'Mutually Assured Destruction: Elizabeth is doing some decoding. Phillip gets back from racquetball with Stan and tells Elizabeth she was right about detecting trouble in the Beeman house. He tells her he missed her while he was gone and they kiss. She tells him there's "trouble at work." They have to stop a Russian assassin who was hired to kill scientists in the U.S. anti-ballistics missile program, but they changed their minds and were unable get back in touch with him. He had a hit list of 14 possible scientist. They don't know when he's going to kill them, or who he is.

Phillip and Elizabeth stake out one of the possible scientists. They've planted a bomb in the man's car. As a warning shot, they kill the car's engine so that the scientist will look under the hood. He does, sees the bomb and gets his wife out just before Phillip detonates the bomb. This was all an effort to get the government to give its scientists some protection.

At the FBI, Gaad briefs his group on the car bomb. Gaad says car bombs haven't been the KGB's M.O.. Agent Amador suggests they put security on more people, but Gaad says they can't chase their tails. He wants to find out who did this.

Elizabeth meets with Claudia and asks why they'd hire an assassin and try to call him off. Claudia tells Elizabeth "the contractor" is from West Germany and gives her some info on a weapons dealer in Baltimore he might be contacting. Claudia then tells Elizabeth that despite the bad blood between them, she feels a "camaraderie" with her. Claudia then tells Elizabeth that Phillip "was with" the agent he was assigned to, but Elizabeth is suspicious, saying she "can think of five different reasons" she'd poison their life. Elizabeth says she asked Phillip. Claudia tells her, "If you start to think of your marriage as real, it doesn't work. The men don't think of it that way. It was an arrangement." Claudia tells Elizabeth that even after what they went through  and Elizabeth's attack on Claudia  she trusts her. Claudia says she's "not so sure" she trusts Phillip.

Elizabeth gets home and finds Phillip asleep on the couch. She stands over him for a moment and he wakes up. She tells him "granny" gave her some info on the killer, then says she's starting to get over the urge to kill Claudia. "She's just doing her job, like the rest of us," Elizabeth says mysteriously.

FBI agents are poring through documents to try to track down the bomber. Amador is bored and wants to blow up the Russians. Gaad calls Beeman into his office. Gaad gives Beeman the keys to a safe house where he and his source (Nina) can have their meetings.

Elizabeth knocks on a door and tells the man of the house (his daughter had initially answered the door) that she knows who he is and what he does, and they need to discuss a few matters. The man tells his young daughter to go up to her room. Elizabeth tells him she needs him to violate his confidentiality because the alternative is "bringing people down on you who will destroy your business." He tells her she's making a serious mistake, and his daughter soon enters the room cocking and pointing a shotgun at Elizabeth. Soon enough, Phillip sneaks up and grabs the shotgun out of the girl's hand and sends her to watch some TV. The man describes the man  6-foot-4, light skin, a little chubby, "friendly guy, actually." He offers to show them pictures. He got pictures of them, too, when they went to his house.

We next see a man somewhat fitting the description who is watching some guys in suits go into a house. He's taking notes in German about the comings and goings.

Phillip is making our with Martha, his FBI contact, but he wants to talk business. She wants to have sex. So they do that. Phillip starts to talk about work. He starts talking about the scientist bombing. She asks if she can help by getting anything that Agent Gaad has on the case.

Nina shows up at the new safe house and Beeman greets her in Russian. Beeman starts to talk bout "whatever happened" the other day. She reminds him that she kissed him, and she kisses him again. And they start getting into it again. She thanks him for getting them a place to meet. She tells Beeman that Arkady is worried at work. She doesn't know what's going on but it seems serious. Beeman asks for more information, but there doesn't seem to be anything out of the ordinary. Beeman tells her he doesn't think he should've gotten her into this. He tells her he can get her out, but it "takes some time." She puts his hand on her breast and says, "I do everything for you. I'm trying my best." He hesitates and tries to say that's not what their affair is about, but she says she's there because that's where she wants to be.

We see the assassin sit next to a woman at a bar. She asks him what his "thing" is, and makes some sexual suggestions. He says he's "much kinkier than that."

Dinner at the Beemans' seems to have some awkward moments, with Phillip seemingly noticing some odd behavior from Elizabeth. Beeman gets a call from work and says he'll be there in about an hour.

Back at home, Phillip asks Elizabeth what's going on. She says she was thinking about when they first met and whether he remembers. He says he was surprised at how pretty she was, then clarifies he was more "relieved" than surprised. She tells him that "granny" said he slept with Irina. She reminds him that she asked him not to lie to her, and he told her to her face that nothing happened. Phillip looks down and says he's sorry.

"I didn't know what to say because I didn't want to lose you," he tells her. "I love you."

She looks at him skeptically and he goes on to say he made "a terrible mistake," and asks if they can try and start over. She says they can't.

"We can do our jobs," she says. "We can fulfill our mission, the reason we were brought to America. But we cannot do this. We will never do this." She leaves.

The woman the assassin had been talking to is now having sex with one of the men in suits the assassin had been watching. She lures the man to the shower of their hotel room and the assassin walks in to survey the room. The man is an FBI agent, which we learn from seeing his badge on the nightstand. The assassin replaces the battery in the agent's radio with an explosive.

At the FBI, Gaad hands Martha some files and asks her to secure them, thanking her for putting in the extra time. After he leaves, she makes copies. She goes on to snoop for more info and Amador surprises her. He tells her she's been looking very nice lately and he's missed her since they broke up. He asks if they can get a drink some time, and she says, "No, thank you." She tells him he's sweet and handsome, "deep down." Then she leaves.

Arkady calls Nina into his office. He starts talking to her about some of the opportunities agents have to sell American goods back home to make some money. She tells him she thinks an assignment in America is a chance "to really accomplish something," and adds, it's "a dream come true."

Phillip shows up at Martha's house. They're soon having sex again. He's not very into it, distracted by the necklace he gave her  which he'd taken from Elizabeth. Later, Martha gives Phillip the information on suspicious foreign nationals who've come through immigration in the last week, correlated with the hotels they're staying in. It's just what he needed.

Later, he and Elizabeth go through the documents and Phillip soon focuses in on the West German assassin.

We next see the assassin in his hotel room watching "The Fall Guy." Phillip and Elizabeth break into his room, pointing guns at him. He calmly asks who they are, figuring that if they were there to shoot him he'd already be dead. They explain that they are there to make sure he complies with the revocation of his assassination orders. He reveals a detonation device, which controls an explosive attached to the wall behind Phillip. He backs away toward the bathroom, pulling his own gun and telling them to put their guns down on the count of three. He gets to two before they shoot him. A gunfight ensues. Before the assassin can regain control of the detonator, Phillip tears the explosive off the wall, tosses it to Elizabeth, who tosses it into the bathroom. The assassin pushes the button, blowing himself to bits. Phillip and Elizabeth survey the scene, then leave.

They calmly walk out while chaos is unfolding at the hotel, and drive away as emergency vehicles are driving back in the opposite direction. Phillip says they can "get past this, it doesn't have to be like this." Elizabeth says, "It is like this  we didn't take a vow to be unhappy."

Nina shows up at the safe house to meet Beeman. She asks him what he did before counterintelligence. She suggests that FBI agents are "cops, policemen in your hearts." She says she wonders if they understand spies. She asks what he wants with Arkady and the others at the Rezidentura. He tells her she now reports to Arkady. She says she might be able to get files for him.

The FBI agent shows up to his shift to protect one of the scientists. The camera keenly focuses in on the agent's radio, which we know has an explosive in it. The agent from the previous shift goes to his car and waits for his partner. Soon after, the place blows up.

Martha looks worried as Gaad finishes a phone call at the FBI. He reports that Leon Billings was inside, too, and didn't survive.

"They're going to pay for this," Gaad say. "I swear to God, they'll pay."

Amador wants to know what's going to happen. He says they have planes and tanks, but no one is using them. Gaad says no one is going to war over this. Gaad adds that "this will not stand."

Elizabeth is doing some more decoding at home in her bedroom. She comes down to the kitchen and tells Phillip that the assassin got one of the scientists and three FBI agents, but doesn't know how. The center wants to know what happened. Phillip says they had bad information and still stopped him, but Elizabeth says they didn't stop him entirely. She says this is their biggest failure in 15 years. It's their job to stop things like this. She says they can't do their jobs if they're emotional. Phillip says emotion had nothing to do with it, but Elizabeth says her head was somewhere else. She says they were never married, "we had an arrangement and it worked."

Phillip tells her he tried. He remembers knowing she was disappointed when she first saw him. He starts to say that if they could change things he would, but Elizabeth tells him they can't change things. Phillip tells him that, given the fact that people get separated all the time, he doesn't think the Center would even care if she didn't want to be married to him anymore.

Gaad leaves the office, saying goodnight to Martha and Amador on the way. Martha leaves and Amador seems to be preparing to follow her.

That night, Phillip is sitting in the living room and hears footsteps. Elizabeth is upstairs, walking in the hallway and going to see her children, who are each sleeping in their rooms.

Martha gets home and Amador is watching.