The series is set during the Cold War and follows Elizabeth and Philip Jennings, two Soviet KGB intelligence officers posing as an American married couple living in Falls Church, a Virginia suburb of Washington, D.C., with their American-born children Paige and Henry.
According to Nielsen Media Research, the episode was seen by an estimated 0.90 million household viewers and gained a 0.2 ratings share among adults aged 18–49.
Stan (Noah Emmerich) and Aderholt (Brandon J. Dirden) continue investigating Martha (Alison Wright), checking her history background.
When Clark Westerfeld is reported as a dead person in Atlanta, Stan and Aderholt disclose their discoveries to Gaad (Richard Thomas), surprising him over Martha's actions.
In March 2016, FX confirmed that the sixth episode of the season would be titled "The Rat", and that it would be written by consulting producer Joshua Brand, and directed by Kari Skogland.
The site's consensus states: "An intense and satisfying episode, 'The Rat' underscores the creators' penchant for uncomfortable, slow-burning, compelling storytelling as the seeds are sown for a key character's demise.
Club gave the episode an "A–" grade and wrote, "'The Rat' is the latest demonstration of Joe Weisberg and Joel Fields' commitment to never getting too comfortable in their storytelling.
The discovery of Martha's betrayal and Philip's decision to bring her in means an altered status quo and a new normal for nearly every character in the show.
)"[10] Genevieve Koski of Vulture gave the episode a 4 star rating out of 5 and wrote, "On some level, Philip means those promises to Martha.
But there's something deeper motivating Philip's behavior: He's protective of Martha, and defiant toward Gabriel and Elizabeth when they question his decision to 'bring her in.'
"[12] Matt Brennan of Slant Magazine wrote, "In 'The Rat,' seeing is indeed believing, and removing the veil lays bare the risk that inheres in the concept of trust.
"[13] Alec Bojalad of Den of Geek gave the episode a 4.5 star rating out of 5 and wrote, "And so Martha is out on her own and the only rat that Philip and Elizabeth are left with is the actual one infected with a mysterious virus that William has brought them.