Elizabeth discovers that the scientist she's bedding is actually trying to create a super-grain, resistant to pests. which can feed the world. The Center, in other words, has been dead wrong about these American scientists are trying to do.
Understandably, Philip is upset, to say the least, when Elizabeth lets him know about this. In a moving scene at the end, Philips says he's been upset about this - killing people - for a long time. Killing an innocent person is even worse. When Elizabeth offers to do this on her own, from now on, to relieve Philip of the burden, he says no, it's us - the two of us, the couple who are Soviet agents, have to stop doing this.
But how will that happen? Though Gabriel is always sympathetic to their plight, he can't even bring himself to let Philip's son see him. Or maybe Gabriel did that precisely because he is indeed sensitive to what Philip is going through, and wants to protect one of his best agents.
Whatever the exact reason, relationships are clearly coming to a boil on The Americans. And that's not even including Stan's new love - who, if she is a Soviet agent, would throw another serious monkey wrench into all of this.
I keep thinking that Philip shouldn't get so close to Stan, shouldn't be tailing him, even when he's in disguise. And that's because I'm convinced that, sooner or later, Stan will discover the truth about his neighbors.
Just a matter of time ...
And see also The Americans: True and Deep ... The Americans 1.4: Preventing World War III ... The Americans 1.11: Elizabeth's Evolution ... The Americans Season 1 Finale: Excellent with One Exception