Sanford Prince (Tim Hopper) tells KGB agent Elizabeth Jennings (Keri Russell) that he has recruited an Air Force colonel named Lyle Rennhull who will give the Soviets important information on the SDI project for $50,000.
Elizabeth brings this information to her husband Philip (Matthew Rhys), who is wary, citing Prince's gambling addiction.
Nina's (Annet Mahendru) suspicions about Stan Beeman (Noah Emmerich) grow and she accuses him of murdering Vlad, which he strongly denies.
Viola Johnson (Tonye Patano), who planted the bugged clock in Weinberger's study in a previous episode, feels increasingly guilty and confesses to Beeman and Gaad.
In April 2013, FX confirmed that the twelfth episode of the series would be titled "The Oath", and that it would be written by Joshua Brand and Melissa James Gibson, and directed by John Dahl.
Eric Goldman of IGN gave the episode an "amazing" 9 out of 10 and wrote, "Suffice to say, 'The Oath' was a great way to set up next week’s season finale.
"[5] Alan Sepinwall of HitFix wrote, "after something of a dud last week, 'The Oath' was pretty fabulous from start to finish – the sort of episode where my notes became littered with profanity as I realized the very risky place so many scenes were heading.
"[8] Carla Day of TV Fanatic gave the episode a 4.8 star rating out of 5 and wrote, "'The Oath' has put all the relationships and informants in a precarious place going into next Wednesday's season finale.