This post contains spoilers from The Diplomat season 3 episode 5 from this point forward.
Following the ambiguous ending of the previous episode, The Diplomat season 3 episode 5 opens with a title card that we're now five months into the Penn administration. During a party where Kate's being greeted by various guests as both "ambassador" and "Second Lady," Eidra's (who hasn't been fired!) watches satellite footage of vehicles pulling into the residence.
Although we haven't been properly introduced to him yet, Kate appears to have built an easy rapport with Callum Ellis (Aidan Turner). Turns out, Eidra and Stuart were covertly working to secure Hal's safe arrival to Winfield in order surprise Kate. When he arrives, he spots her hand placement on Callum and isn't pleased. And when Kate finally sees him, let's just say her reaction is awkward.
After her tense exchange and reunion with Hal, Kate takes the microphone to introduce Callum with some light jokes pretending how she's annoyed by him. She cuts her address short, seemingly to avoid further frustrating Hal. Kate steps aside to call Stuart to confront him about Hal surprising her, and he reveals the intention was for their anniversary. She's a little more than irritated.
Hal discovers Kate's new relationship with Callum Ellis
Hal sniffed out immediately that Kate and Callum have been romantically involved and she assumed that Hal would be okay with it given their arrangement. Well, he's not. He has a drink with Callum and Kate and pushes for more information. Callum reveals that Moscow has lost contact with a submarine asset, and he has asked for the North Sea's marine sensor data to help find the nuclear-powered submarine. When Hal brings up Kate and Callum's relationship, she makes Callum leave.
Kate and Hal finally have it out, and Hal wants Kate to make a statement to the CIA about the manner of her relationship with Callum. He seems to think that it could be a threat to national security and a cost to the American government. They don't reach any resolutions about her "affair," and Kate rushes downstairs to the library and breaks down crying on the floor.
Eidra discovers the truth about the carrier attack
Eidra comes to Stuart and admits that she's drowning with her work and wanted to have a drink with him. He turns her down and suggests that she should speak to Hal about her situation. She first comes to Kate, which gives her the opportunity to be honest with Eidra about her marriage with Hal. Kate misunderstood the nature of Eidra's conversation with Hal. Speaking of Hal, he's still mad at Kate, and she wants to talk with him before their televised interview.
The interview is abruptly paused when Kate's handed a note and they're pulled into a private room. Kate lays out the situation about Eidra's walk-in with a man who worked for Lenkov and claims to know that America was behind the carrier attack. Eidra's waiting for them in the Reading Room and reveals the claim checked out. Before they leave to brief Penn, Hal breaks the truth to Eidra. Stuart's stood up for his drink with Eidra, who's busy in the air strategizing with the vice president.