In early January, 49 BCE, the Roman General Julius Caesar marched his army through Gaul and came to the small river that marked the northern border of Italy: the Rubicon. Marching armed soldiers into Italy was akin to insurrection. On the shores of the shallow river, Caesar proclaimed alea iacta est (the die is cast) and led his army into Italy. This singular action marked the moment that Caesar declared war on Rome. Crossing the Rubicon is now synonymous with an irreversible course of action. 

Star Trek Discovery: Rubicon Recap

This season of Discovery continues to focus on the Dark Matter Anomaly (DMA) and the emergence of a new and powerful species: species 10C. In this week’s episode, we follow Book (David Ajala) and Ruon Tarka (Shawn Doyle from The Expanse and House of Cards) as they seek to execute their rogue plan to destroy the DMA using stolen Starfleet equipment (the spore drive) and a weapon of mass destruction (an isolytic burst). Even knowing that the DMA is not killing intentionally (but instead seems to be a mining instrument), Book is still bent on revenge; he sends Michael an encoded message telling her this before heading to fuel their weapon.

In Hollywood storytelling fashion, in spite of the fact that Michael’s judgment is clouded when it comes to Book (he is her boyfriend after all), somehow Discovery, led by both Michael and Suru, are sent after them. At least, in this case, Admiral Vance has a plan to ensure the mission is not compromised. He sends along Commander Nhan (Rachael Archeril) – the former “no-nonsense” security officer of Discovery, who we last saw piloting the USS Tihkov back to her home planet of Barzan. I loved Nhan on Discovery and am glad that she is back. She is never afraid to make the hard calls and that’s exactly why Vance wants her on Discovery; as a Barzan, it is “duty above all else.”

Now fully prepared, Discovery heads off to track down Tarka and Book, informing the bridge crew that Commander Nahn is there to ensure they fully execute their mission. Discovery first tries to stop Book and Tarka as they are fueling their isolytic weapon (a weapon so powerful that it was banned by the Second Khitomer Accords). However, after springing one of Tarka’s booby-traps, the crew barely escapes with their lives. Book and Tarka, having fueled their weapon, head off to track down the DMA. They have made it clear that they are deadly serious about executing their plan to take out the DMA, regardless of the cost. 

Book’s ship is now after the DMA with Discovery in hot pursuit. When they arrive in the region, Discovery is unable to cloak and its sensors go haywire due to the interference from the DMA. As Discovery and Book/Tarka enter a cat and mouse game of pursuit, Commander Nahn pulls Michael and Suru into the ready room to share with them some information. There is a weak point on Book’s ship that they can leverage. If they hit the right spot with a photon torpedo, they will trigger a catastrophic failure of the spore drive. The only problem is, it might also take out Discovery.

While Michael clearly doesn’t want to kill Book, she tries to argue that the risk to Discovery is too great — Starfleet needs its spore drive technology. The two disagree and as Nhan attempts to pull rank, Saru quickly defuses the situation but it’s clear that if it comes down to a game-time decision, Nhan will destroy Book’s ship.

Will they destroy each other?

A similar argument is taking place between Tarka and Book. Tarka tells Book that he needs to prioritize destroying the DMA and not the welfare of the crew of Discovery. Their weapon is finished, so they load it into the torpedo bay and continue to search for the DMA controller. Before they can fire, however, Discovery appears and the two ships attack one another. Book tries to simply send warning shots, but Tarka quickly takes over and fires a full-sweep of photon torpedoes, damaging Discovery.

Nhan uses this as justification to issue the destruction order. However, Michael successfully argues for one last chance to talk Book out of it. She takes a single shuttle out to Book and tells him that Discovery has learned that it will take the DMA a couple of weeks to mine all of the Boromite in the region. It will stay in this uninhabited area, giving the Federation time to make first contact with species 10C. Against Tarka’s wishes, Book agrees to wait. 


Pictured: Sonequa Martin-Green as Burnham and Rachael Ancheril as Commander Nhan of the Paramount+ original series STAR TREK: DISCOVERY. Photo Cr: Michael Gibson/Paramount+ © 2021 CBS Interactive. All Rights Reserved.

Tarka, however, disagrees. After giving a long-winded speech about the mathematical concept of expected utility, he crosses the Rubicon — launching the weapon into the DMA controller. Discovery cannot beam it out (too much interference) and both ships need to flee quickly or they will be destroyed. The explosion will destroy the DMA and possibly ignite conflict with an unknown (and powerful) alien species. Tarka attempts to retrieve the DMA’s power source (something he plans to use to enter the alternate universe he explored with his best friend when he was still a slave). To Tarka’s dismay, the power source is not on the controller but rather on the other side of the wormhole! 

With the DMA destroyed, Starfleet fast-tracks plans for first contact hoping to avoid retaliation with a species far more advanced than they are. As Michael laments the loss of Book (who is now a criminal), she and Nhan reflect on their experiences as strangers in their new land. Nhan says she may come back to Discovery one day (I really hope she does). They are interrupted, however, with a report that the USS Mitchell, patrolling the area of the explosion, has reported a new DMA in the exact location of the one destroyed. Species C10 is back. 

Star Trek Discovery S4E09 Rubicon Review

Like many viewers, I have found this season of Star Trek: Discovery promising, but falling a little flat. The DMA is definitely a better adversary than the Burn. The Burn, after all, took place in the past whereas the DMA is an active threat. The show does a good job of exploring the moral ambiguity of the decisions of its characters; the bridge crew argues over whether or not Book’s motives are just and the lack of justice for his people. 

At the same time, I feel that Discovery misses the opportunity to go further into exploring its characters. Tarka, for instance, is fascinating. He’s a more arrogant (and brilliant) version of Stamets. Yet, being Risian, his behavior is often surprising. The show hints at his motivations (slavery, the loss of a loved one, a desire for a world without suffering), yet fails to truly delve into his character in a meaningful way. While I love Dr. Culver, I still question the decision to make him an impromptu ship’s counselor, and the parallels they draw to healthcare workers’ stress during Covid-19 feels forced and unnecessary. 

Rubicon does the best job so far of trying to get this season of Discovery back on the tracks. I hope that the rest of season 4 can follow suit. 

Thanks for reading. Make sure to comment your thoughts on this season of Star Trek: Discovery. And stay tuned to THS for more reviews!