Written by Lindsey Allen, Christopher Markus, Stephen McFeely, Stan Lee, and Jack Kirby
Directed by Stephen Williams

Although the viewing audience knows Peggy is on the same side as the SSR, she’s managed to keep her work trying to clear Howard Stark’s name from her co-workers, until now. This week, Peggy is exposed and everything comes to a head. The episode title is a cryptic reference to a real Cold War Soviet spy ring that used ASINTOER (mnemonic “A sin to er(r)”) as one of their coding keys.

A Sin To Err opens by showing how “bad” the Leviathan organization is, by showing a man who wishes to remove his daughter from the “program” being executed, along with the promise that the entire family will be executed as well. Leviathan seems to be something like the mob.

Chief Dooley (Shea Whigham), Agent Carter (Hayley Atwell), and Jack Thompson (Chad Michael Murray) interrogate Doctor Ivchenko (Ralph Brown) whom they withdrew from the training facility in Belarus. Dr. Ivchenko seems to be willing to tell them what he knows. He tells them about the program to train young girls to be operatives and Leviathan. Peggy tells Dooley what she has put together about the situation, and he reluctantly admits that her conclusions have some merit.

Peggy meets clandestinely with Jarvis (James D’Arcy) and tells him her theory about Howard (Dominic Cooper) being compromised due to a woman who was really a Leviathan asset. She asks him for a list of the women Howard was involved with recently, and Jarvis muses that might take some time. They visit a jeweler for a list of women who have received a particular gift from him.

Meanwhile, Daniel Sousa (Enver Gjokaj) starts following up on his suspicions that Peggy might be the mysterious woman who has turned up in various places during the investigation. Peggy’s duplicity in the SSR comes to the forefront. Dooley is stunned that she managed to escape a team of agents sent to bring her in and now considers her a fugitive. The truth is, Sousa couldn’t bring himself to shoot her.

Meanwhile, Chief Dooley is chatting with their informant who might not be helping them as much as it seems. There’s a connection there to Dottie (Bridget Regan) and Leviathan.

Once she has eluded her fellow SSR agents, Peggy races back to The Griffith to retrieve Steve’s blood from where she hid it. Jack and Daniel are hot on her tail. She hides on the ledge outside her window while they ransack her apartment. She nearly manages to escape, but Dottie finds her and tries to kidnap her. The agents catch up with them after Peggy is knocked out and take Peggy in. Dottie disappears.

What’s interesting in this episode is that Peggy makes the same mistake her male coworkers have been making with her. She sees the women at The Griffith as just women and never considers that they could be something more. This is why Dottie fools her right to the very end when Dottie uses Peggy’s own weapon on her.

Angie (Lyndsy Fonseca) does a great job getting the agents off Peggy’s trail (briefly) at The Griffith. She plays both sides here, at one point getting in a dig about Peggy’s lunkhead male co-workers, then using tears when they are getting too close to Peggy. It works predictably on the men, just as Peggy bringing up “female problems” managed to get them to refrain from probing too deeply earlier in the season.

Dr. Ivchenko, who seemed to be one thing after the previous episode is revealed to be quite good at what he does. He manages to get Dooley to talk to him and open up about problems on the home front. During the conversation, it appears he is hypnotizing Dooley, although Sousa interrupts him. For the time being, he moves his target to a different agent and shows what he is capable of. The story advances nicely as viewers get more of an idea of what Leviathan is up to. The intrigue is building quite a bit, while at the same time keeping the tension high. A revelation here brings new questions, How will Agent Carter prove her innocence and her good intentions from the beginning?

Previous episode in the series (link): Agent Carter: The Iron Ceiling

Next episode in the series (link): Agent Carter: Snafu