The Diplomat – Season 3 Episode 8

Published: Oct 20 2025

The opening of Episode 8 of The Diplomat season 3 unfolds with our key characters congregating at Chequers, a setting imbued with an understandable tension, as Hal and Kate strive to maintain their facade despite their separation. Callum's presence adds to the complex dynamic, though Kate swiftly clarifies the situation with Hal, revealing his role in the delicate negotiations surrounding the British submarine fiasco.

The Diplomat – Season 3 Episode 8 1

Trowbridge and Grace Penn's meeting is fraught with a thin smile and an undercurrent of unease. However, the most revealing conversation transpires between Grace and Todd, who despite their loud arguments and oyster shucking mishaps, still harbor a deep love for each other. Todd perceives a hint of something more intimate between Hal and Grace, which Grace dismisses lightly but their frequent interactions suggest otherwise.

Dennison's arrival adds another layer to the intrigue. When Stuart informs Kate of Dennison's presence with his partner, her immediate assumption is that she might be pregnant. However, it turns out that Dennison and his girlfriend Thema are actually married—a swift development that fortunately does not detract from the natural flow of their interaction.

The pivotal meeting between Grace Penn and Nicol Trowbridge delves into the sensitive topic of the disabled Russian submarine, the Poseidon, an underwater drone powered by a small nuclear reactor, armed with a nuclear warhead, and designed to contaminate a vast area with radioactive fallout. Grace urges Trowbridge that involving the Chinese in this endeavor would be a misstep, reinforcing her determination to assist in its retrieval.

Kate's plan unfolds with a hunch of uncertainty, as she rises from her seat, disregarding the words of warning, convinced of her friend's deception. Her mind races to find an ally who can sway him from this course of action—Callum, a delicate tangle in the web of loyalty and consequence. His involvement carries a heavy price, with the risk of his sources being endangered. The tension in the air is palpable as Callum, with a skeptical gaze, questions if this daring move was Hal's idea. It wasn't, but the elephant in the room lingers, preventing a smooth progression for the duo.

As dinner hour approaches, the atmosphere is strained. Small talk and forced attempts to fill the silence only serve to heighten the tension. But it's Callum who breaks the ice, speaking with Kate outside and agreeing to inform Trowbridge of the Russians' approach regarding Poseidon. This could be a game-changer in convincing him and moving forward. Kate vows to protect Callum and his source, a promise that echoes her previous actions in the Eidra situation—but will she be able to keep it?

Hal, on the other hand, sees this as a poor decision, convinced that her loyalty was swayed by his heroic act of protection without realizing the idea actually originated from her.

An alternative plan emerges from Hal and Kate, presenting Grace with the notion of deploying an American submarine to take pictures of the sub. Given its proximity to the UK waters within three hours' reach from a submarine off the coast of Germany, this would provide undeniable evidence of the weapon's existence. However, this option entails double-crossing Trowbridge and operating behind his back. With the current frosty dynamics, this may not be the most prudent move.

As Kate and Dennison cross paths out of the room, a subtle moment of connection transcends between them, with Dennison unaware of the separation between Kate and Hal. His words are filled with a mix of inspiration and regret, his heart moved by their resilience and determination to recommit to their relationship, even amidst the challenges they face. He reflects on his own relationships, particularly after his wife's suicide, exhorting patience for both himself and Hal. With a gentle squeeze of her hand, he walks off to join his wife in bed, hoping she is asleep so as not to disturb her with his snoring—a reason he's out alone in the first place.

Meanwhile, Trowbridge's decision is questioned as Grace presents him with the photos. While Todd remains suspicious of Grace and Hal's closeness, Kate brings good news to Callum, assuring him that he doesn't need to sacrifice his career. Grace pleads her case, admitting that while this could be seen as an act of war, she is willing to take this risk in the hope that it will be the first step towards mending the broken ties between them and moving forward together.

Trowbridge initially refuses to let the Americans take the sub, but Kate suggests an unconventional solution: burying the whole thing in concrete to ensure no one can have access to the weapons. Thankfully, he agrees to this idea, opening a door for a potential resolution.

The explosive revelation unfolded like a crescendo, as Kate's musings after her earlier conversation with Dennison coalesced into a realization that Callum's allure paled in comparison to the prospect of a journey with Hal. She found herself yearning for a flight back to the United States on Air Force Two, even imploring him to escort her.

However, the tranquil narrative was shattered by the abrupt arrival of Callum, bearing startling news: the Russians had discovered the sub and had taken possession of Poseidon, with the radiation levels around it plummeting.

As Kate spoke to Todd outside, the words "close relationship" and "quiet plotting for world domination" between Hal and Grace echoed like a sinister lullaby. The penny dropped for Kate; Hal and Grace had taken Poseidon, effectively committing an act of war. The Russians would perceive this as an act of aggression by the UK, leading to an imminent attack.

Hal's reply cut through the air like a knife: "Kate, you will keep your silence," confirming the direst of her fears. The scenario painted a picture of impending chaos and international intrigue, with each word laden with the weight of potential disaster.

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