The Diplomat Season 3 Ending Explained: Who Took Poseidon?

The third season of Netflix’s ‘The Diplomat’ picks up in the immediate aftermath of the Season 2 finale. The last we saw of Kate Wyler, she was confronting Vice President Grace Penn about her actions with HMS Courageous while speaking of her own desire to become VP. Unbeknownst to her, her husband, Hal, patches a call to the White House, getting a direct line to President Rayburn, whom he told everything about Grace’s betrayal. Hal knew it would have a significant effect on the President, but he didn’t anticipate that the news about his VP could kill him. Now that Rayburn is dead, Grace is the new President, which leaves Kate’s and the country’s fate hanging in the balance. SPOILERS AHEAD.

The Diplomat Season 3 Recap

Despite their rivalry, when Grace becomes President, Kate is nothing but helpful to her. One of the reasons why she wants to be in Grace’s goodwill now is because she knows that someone level-headed is needed to be her deputy, to prevent her from making the kind of decisions that led to the HMS Courageous incident. Everyone thinks that Kate is the best person for the job, but Grace flips the board by nominating Hal. This breaks Kate’s heart, but she steels herself, especially now that she knows Hal will need all the help he can get. His nomination is a surprise to him, too, and he promises Kate he will get her a job worthy of her. He comes through on his promise, but Kate is not ready to leave London yet.

So, she decides to juggle her job as an ambassador with her role as the Second Lady. This puts many miles between her and Hal, but they have already become so distant that being on different continents feels like a good choice. Both agree that they will keep the facade of the marriage alive for public image, but in personal terms, they are separated. Back in London, Kate goes back to her job as the ambassador, which puts her in touch with a British spy named Callum Ellis. He tells her about an abandoned Russian nuclear submarine off the coast of Britain, which needs to be taken care of.

Interestingly, he came to Kate first with this news, and now they are working together to figure out this mess. Their professional collaboration turns into a romance, which they keep, or at least try to keep, a secret from others. Meanwhile, things get complicated when the secrets about HMS Courageous are threatened to be brought to the surface by a Russian source. Culling this issue turns into a blunder that could cost the country everything. But Kate, in her never-ending streak of wit and wisdom, comes up with a clever plan. It isn’t until much later that she discovers she had been manipulated by Hal into doing something that could have biblical implications for her as well as the country.

Does Trowbridge Accept Grace’s Help?

The attack on HMS Courageous had been a critical point in Nicol Trowbridge’s administration in the UK, and he, like every other Briton, had been enraged and infuriated with it. He did everything in his power to bring the guilty party to justice. When he found out that Margaret Roylin, who had been his mentor and his confidante over the years, was involved in it, he had made up his mind to have her killed as well. He never got to that point because Roylin killed herself, but it shows just how much anger Trowbridge held. And then, the Americans tell him that Roylin collaborated with the late President Rayburn.

Not only that, they ask him to keep Rayburn’s name out and put the entire blame on Roylin, at least for the time being. This broke Trowbridge’s trust in his American counterparts. He felt cheated by them, especially since he found out that they’d known about it for a long time but gave the information only after the Russians forced their hand. So, in the press conference, Trowbridge tells the truth about Rayburn and cuts off all communication with the Americans. Their credibility has been so tarnished that when they tell him that there is a nuclear submarine with the infamous and not-so-mythical Poseidon a few miles away from the British coast, he refuses to believe them.  He knows the part about the submarine, but he thinks Poseidon is a lie.

Since he still needs someone’s tech to get rid of the sub, he turns towards the Chinese. This alarms the Americans, because they know that this move would put Poseidon in their hands. In the end, Grace presents an olive branch, trying to make Trowbridge see sense and offering America’s help in disposing of Poseidon without causing any trouble for the UK. He stands his ground and refuses to collaborate with them, but eventually, when proof of Poseidon is put in front of him, he concurs that the Chinese cannot be allowed anywhere near it. However, he doesn’t want the Americans to have it either. This is when Hal and Kate propose the idea of Runit Dome. Instead of letting anyone have Poseidon, it should be buried under concrete at the bottom of the ocean. This satisfies Trowbridge, and he agrees to a truce.

What Happened to Poseidon? Who Took It?

The myth of Poseidon had traveled the circles of intelligence agencies over several years, but it was not believed to be real. So, when Trowbridge is told about it by Americans, no less, he believes that this is yet another lie they are concocting to make themselves appear indispensable to the UK. To prove it, Kate suggests sending a drone down to the bottom of the ocean, which could take pictures of Poseidon. Since it is known to have a characteristic hull, it would be unmistakable in the pictures. Once Trowbridge knows the threat is real, he wouldn’t think about going to the Chinese again. The problem is that it would require the US Navy to enter the UK’s waters without permission, and it could be perceived as an act of war. But that is a risk they have to take, and once Poseidon’s presence is proven, Trowbridge would be too caught up with dealing with the nuclear threat rather than chiding America for bringing their ships into the UK’s waters.

The plan works. When the photos are placed on Trowbridge’s desk, he immediately rethinks his strategy of going to China. When he questions why Americans, and not the Chinese, can be trusted with Poseidon, Kate gives him the option of letting the weapon rot at the bottom of the ocean since no one should have that kind of power. He listens to her, and for a moment, all seems well. But just as everyone is about to depart, Callum tells Kate that Poseidon has gone missing. The radioactive readings of the area have dropped dramatically, which can only happen when one of the two devices has been removed. This is alarming news, especially if it means that the Russians have taken it. Kate immediately relays this to Hal, who talks with Grace.

While the President and her VP are deep in discussion, Grace’s husband, Todd, asks Kate if she is okay with Hal and Grace’s successful and somewhat oddly close professional relationship. At first, she dismisses his concerns, believing that he is alleging a romance between the two. But then, she realizes that it is more than that. They are not secret romantic partners, but co-conspirators, which is worse, because it means that they are the ones who stole Poseidon. She immediately confronts Hal about it, pointing out that even though Grace sent a submarine to take the photos, she told Trowbridge that the drones were used for getting the proof. The timing of Poseidon’s disappearance is also very suspicious, and not shockingly, Hal admits that they did it. America has Poseidon, but she cannot tell anyone about it.

Do Hal and Kate Get Back Together? Does She Break Up With Callum?

Earlier in the season, when Grace starts to have second thoughts about making Hal the VP, Kate tells her Hal tends to surprise you at the most unexpected of times. While it was meant as a compliment, it is proven in the most uncomplimentary way at the end when the truth about Poseidon comes to light. Kate has no doubts that it is Hal who proposed the idea of stealing the weapon from right under Trowbridge’s nose. He would have sold it as insurance, just in case the British PM still refused to join hands with them. In that case, Poseidon would be out of the hands of the Chinese, and the Americans would have nothing to worry about. If Trowbridge accepted the olive branch, it would bridge the divide between the two countries.

Of course, Hal, being Hal, doesn’t stop to think about the consequences of his actions. He doesn’t wonder what happens when the Brits find out about it, which they are bound to, at some point. Grace thought no one would find out about HMS Courageous, but despite all efforts to push it down or to shift blame to someone else, the truth, or at least part of it, did come out. What happens when Trowbridge finds out that, under the guise of helping them, the Americans have once again duped them? This makes Kate realize that, once again, she may have placed too much faith in Hal and forgotten for a minute how flawed he actually is. Minutes before she discovered his treachery, Kate patched up with him, apologizing to him about wanting to go their separate ways and about her affair with Callum.

She wants them to be together again, and Hal welcomes her with open arms. Just as they are about to step out, Callum shows up, and it is presumed that Kate will use this time to break up with them. But then, he tells her about Poseidon, and the whole thing comes crashing down on Kate again. Once again, Hal has subverted expectations in the worst of ways. Just when she thought she could love him again, he went ahead and did something so spectacularly blunderous that she is forced to reconsider everything, including their marriage. So, while she may have chosen Hal over Callum, the road is not going to be any smoother for them. Moreover, she still hasn’t technically broken up with Callum, and given Hal’s actions, she might end up seeking comfort and some sanity in Callum’s arms after all.

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