Spoilers ahead!

The fourth season of The Diplomat has reached a point where it is becoming increasingly difficult to identify who is genuinely trying to prevent a war and who is simply concerned with preserving their authority. Grace Penn (Allison Janney) threatens to send warships against the Russians, Bethan Vaughn (Jodie Whittaker) refuses to yield to American pressure, and Kate Wyler (Keri Russell) finally begins asking a question that should have occurred to her long ago: to what extent has she become complicit in the very decisions she so strongly condemns?

The sixth episode picks up the crisis surrounding the sunken Russian submarine and the Poseidon nuclear weapon, secretly removed by the United States. Britain’s new prime minister has authorized the Russians to recover the bodies of their dead sailors. It is an understandable decision from a humanitarian perspective, but it represents a potential disaster for Washington. Once the Russians reach the submarine, they will discover that their weapon has disappeared.

Grace Penn has no intention of allowing that to happen. During a video conference with Kate, Hal Wyler (Rufus Sewell), Billie Appiah, and Miguel Ganon, the president proposes a solution as simple as it is dangerous: if Vaughn refuses to cancel the Russian operation, the United States will send warships to stop it.

It is difficult to imagine a more aggressive strategy for resolving a crisis created by the Americans themselves. First, they steal the weapon. Then, they lie to their allies. Finally, they threaten military force if the British refuse to help conceal what happened.

Kate immediately understands the seriousness of the proposal. A naval operation of this nature could provoke a confrontation with Russia and permanently damage relations between Washington and London. But Grace ends the meeting before any opposing arguments can gain traction.

The president is not interested in discussion. She is interested in obedience.

After the meeting, Kate speaks with Todd Penn (Bradley Whitford). The president’s husband is still trying to understand what has happened to Grace since the assassination attempt. He acknowledges that the woman he married seems increasingly distant and does not know how to help her. Kate, meanwhile, attempts to explain why she considers the president’s decisions so dangerous.

It is interesting how Todd, initially presented almost as a comic inconvenience, begins to take on a more significant role. He knows Grace intimately but does not understand the logic behind her political decisions. Kate understands that logic, although she is frequently unable to change it. The two eventually find a kind of common ground in their shared inability to influence the president.

Meanwhile, Stuart Hayford and Eidra Park face yet another relationship crisis. This time, the discussion begins with a marriage proposal delivered so pragmatically that it practically eliminates any possibility of romance. Eidra sees marriage as a convenient solution to the problems they face. Stuart, naturally, would like to believe there is something more meaningful behind the decision.

Their relationship remains one of the few attempts the series makes to show characters concerned with something other than the next international crisis. But it is also amusing to watch how they manage to turn a conversation about love into something resembling a bureaucratic negotiation.

The more serious problem, however, emerges inside the embassy itself.

Frances tells Stuart that she overheard Kate admitting she blackmailed Nicol Trowbridge using compromising footage involving Margaret Roylin. It is a serious revelation. The American ambassador not only contributed to the downfall of a British prime minister but resorted to a method that could hardly be defended as diplomatic.

Stuart is deeply shaken. After all, he has always believed that Kate, despite her excesses, represented a more ethical alternative within the American political establishment.

The situation becomes more complicated when Kate decides to expand Todd’s security clearance, allowing him access to highly classified information. Her intention is to turn him into someone capable of influencing Grace. The president approves the arrangement, although she displays little confidence in her husband’s usefulness.

Todd, however, seems to have found a new mission. During a conversation with Grace, he discovers that she wants him to remain in London as a show of strength against those who attempted to assassinate her. The president also wants him to serve as her eyes and ears.

It is a considerable responsibility for someone who, until recently, seemed primarily interested in escaping the White House.

Stuart confronts Kate about the blackmail against Trowbridge. Meanwhile, he and Eidra reach an understanding about their relationship: they will give themselves one year to decide whether they intend to marry or go their separate ways. The proposal comes with an improvised romantic gesture that substitutes office supplies for flowers. It is one of the episode’s few genuinely tender scenes.

But intimacy also makes it easier for information that should remain restricted to circulate. Stuart tells Eidra what he has discovered about Kate, and the two begin to understand the full extent of the problems facing the embassy.

Kate realizes she can no longer keep everything hidden.

During a meeting with Stuart and Eidra, she finally decides to explain the operation involving Poseidon, the blackmail against Trowbridge, and Grace’s responsibility for the earlier attack on the British warship HMS Courageous.

What makes the conversation important is not simply the revelation of the facts. It is Kate’s recognition that she may have lost the ability to distinguish between following orders and participating in a system that has become fundamentally compromised.

She asks them whether the threat Grace intends to make against the prime minister crosses an unacceptable line.

Their answer is yes.

And, for the first time in quite a while, Kate seems genuinely willing to consider what to do with that information.

The solution involves preventing Todd from attending the meeting with Vaughn. Stuart arranges an outing to a concert, while Kate heads to meet the prime minister accompanied by Eidra.

Bethan Vaughn does not make things easy. She explains that the Russians intend to recover their dead and that preventing the operation will not make the problem disappear. Kate proposes alternatives, including an American or British mission to recover the bodies and permanently restrict access to the submarine.

The proposal makes sense. It could prevent the Russians from discovering Poseidon’s disappearance and reduce the risk of military confrontation.

But Vaughn does not trust the United States.

And why should she? The American administration has already demonstrated that it regards British sovereignty as a negotiable detail.

Kate insists, tries different arguments, and searches for a solution that does not involve military threats. The prime minister, however, rejects her proposals.

Later, during a meeting with the American team, Kate announces that she has delivered Grace’s ultimatum and that Vaughn has agreed to cancel the Russian operation.

It is a statement that ends the episode with a fundamental ambiguity.

The sixth chapter represents a change in Kate’s trajectory. Until now, her job seemed to involve managing the consequences of Grace and Hal’s decisions, even when she strongly disagreed with them. But her conversation with Stuart and Eidra raises the question of her own personal responsibility.

Because there is a difference between working for an administration whose decisions we disapprove of and actively contributing to actions we consider unacceptable.

Kate has spent much of the season trying to convince others that they have crossed the line. Now she must decide whether she is prepared to recognize her own.

And perhaps that is, finally, the most important diplomatic question of the fourth season.