Watson wrapped its two-season run on May 3 after being canceled in early 2026.
Key Points
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The final episode finds Watson reuniting with Holmes amid his struggles with a brain tumor.
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Eddie Izzard guests as Sebastian Moran, an infamous villain from the Sherlock Holmes canon.
Watsonis one of the stranger procedurals to emerge over the past several years, reimagining the canon of Arthur Conan Doyle's Sherlock Holmes books and stories inside an investigative medical drama. But, as its title implies, the focus isn't on Holmes, but Dr. John Watson (Morris Chestnut), the detective's loyal confidant. Along with his fellow doctors at the Holmes Clinic in Pittsburgh, Watson treats patients with baffling, often misleading symptoms.
Watson's first season began withHolmes' death, but the detective resurfaced in season 2 (played by Robert Carlyle). As the season unfolded, however, we came to learn that this version of Holmes was a hallucination brought on by the tumor in Watson's brain.
But season 2's penultimate episode threw us quite a twist when the real, non-imaginary Holmes turned up in the clinic with what appears to be a case of amnesia. Our heads are spinning, too.
The final episode of season 2, "Cobalt Fissure," will be the last episode ofWatson, as the series was canceled by CBS earlier this year. Below, we break down how the series says farewell to Chestnut's Watson while folding in another character from Doyle'sSherlock Holmesstories.
What's wrong with Holmes?
The episode begins with Watson being prepped for surgery at a clinic in Baltimore to deal with the glioblastoma in his brain. But he flees upon hearing that Holmes, who he's been hallucinating all season, has appeared back in Pittsburgh.
Holmes' symptoms — memory loss, dehydration, hypotension, elevated liver enzymes — confound Watson and the rest of the doctors, who spend much of the episode debating various treatments and potential diagnoses.
The secret to Holmes' condition, however, lies in an old case he and Watson investigated years prior. They reminisce about it as Holmes' memory returns — a three-day pursuit of an adversary led them to a weapons testing site populated by soldiers clad in biohazard gear. It was radioactive, and both Holmes and Watson's proximity to it contributed to their individual ailments.
Watson confirms this by testing a sweat-soaked towel carried by Holmes. The results point to what Holmes describes as a genetic alteration — "I'm a mutant," he declares — and the treatments appear to be working by episode's end.
Tragically, as Holmes gets better, Watson gets worse. His tumor is giving him seizures that grow in severity throughout the episode.
Who is Sebastian Moran?
There have been whispers of Sebastian Moran, an acolyte of Holmes and Watson's nemesis Moriarty (Randall Park), throughoutWatson, but it's only in the series finale that the killer actually surfaces. Fans of the Sherlock Holmes canon will be familiar with the character, as he plays a similar role for Moriarty to the one Watson plays for Holmes.
Eddie Izzardplays the loquacious Moran with a slimy charm, and it's a shame we won't get to see more of the character. In this episode, he shoots and kills an oncology nurse in a random attack that's meant to get Watson's attention. Why? Honestly, it's all a bit confusing — and we wouldn't be surprised if this storyline was reworked upon news of the show's cancellation.
Basically, Moran says that he's the one who dropped Holmes off at the clinic. See, he's been holding Holmes hostage and using the detective to help carry out his own nefarious schemes. There's been a "power vacuum" since Moriarty's death, he says, and he's trying to fill it. But Holmes' sickness has made him "not quite so useful," so he needs him patched up and delivered back to him.
His murder of the nurse is followed by threats against Dr. Mary Morstan (Rochelle Aytes), Watson's ex-wife. If Watson's team involves the police, he says, he'll have his cronies kill her.
How is Moran foiled?
Holmes doesn't seem to remember his work for Moran, but he remains familiar with the villain and helps Watson and Shinwell Johnson (Ritchie Coster) in their efforts to find his hideout.
Moran is dyslexic, Holmes explains, and uses the letter "x" as a means of simplifying confusing letter patterns. X being a "safe" letter for Moran, Holmes suggests that he could be hiding out under a fake name that includes multiple x's.
Shinwell finds Moran in a nearby hotel, where he's checked in with the name Alexander Cox. Shinwell, as fans of the series may recall, has a personal vendetta, as he believes Moran murdered William and Nancy Evans, a couple that cared for him like a son. But Moran claims he never killed the Evanses, though he will if Shinwell rats him out.
This puts Shinwell in a tough spot. A former debt collector with a violent past, he's reformed himself in recent years. He even promised his new fiancée, Carlin (Margot Bingham), that he was leaving that part of his life behind. Does he preserve his innocence — or make Moran pay for his sins?
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When next we see Shinwell, he's approaching Carlin at the clinic with a sack of Moran's teeth. Yes, he flexed some of his old muscles to force Moran to give up the men monitoring Morstan — and the location of the Evanses. He confesses this to Carlin, but reveals that instead of finishing the job himself, he gave up Moran to the authorities.
"Yeah, I wanted to carry on. Good god, I wanted to carry on. But I didn't," he says. "No one is damaged beyond repair. It's just, I can't lose this..."
She forgives him.
What else happens in theWatsonseries finale?
Dr. Sasha Lubbock (Inga Schlingmann) has spent much of the season being deceived about the identity of her birth mother, sending her into something of a tailspin. While Dr. Ingrid Derian (Eve Harlow) is able to point her in the direction of her real mother, Sasha is still nursing some deep wounds.
It makes sense, then, that she'd choose to be alone in the finale. After Dr. Stephens Croft (Peter Mark Kendall), with whom she's had a tumultuous relationship, tells Sasha he wants to commit and give her the wedding and family of her dreams, she rebuffs him.
"I've been a bit of a fool for a good while now," she says. "I need to change some things. I don't know how I'm supposed to be in the world. I don't know who I am, and if I don't know who I am, how am I supposed to know who to be with? Stephens, I'm happy you know what you want right now, it just shouldn't be with me."
Ingrid, meanwhile, appears to have gotten away with her murder of Beck Wythe (Noah Mills), the man responsible for Sasha's deception. While Det. Lestrade (Rachel Hayward) has doubts that the slaying was in self-defense, as Ingrid claims, she has no hard evidence. The last we see of Ingrid, she's back in group therapy for antisocial personality disorder.
Does Watson die?
Watson is able to save the life of his old mentor, but not before severely endangering his own. After suffering multiple seizures, he's prepped for surgery to address his brain tumor. Before he goes into surgery, his colleagues shed tears as they thank him. There's a good chance he won't survive the operation.
Morstan, his ex-wife, tells him how her "entire world changed" the day she met him. "I am in that operating room with you, John. Every room you walk into ever, I'm there."
Stirred by her words, he wakes and recalls the moment earlier in season 2 when he walked in on her kissing her new boyfriend, Josh (C.J. Lindsey).
"I was there to say I love you," he croaks. "I have this picture of you and me and we're living on Baker Street in London and we're having breakfast but we're not talking because we don't need to talk. We have everything we need."
"You're going to be okay, John," she says. "You have to be because I can't imagine a world without you."
So, does Watson survive the operation? Well, that depends on how you interpret the ending. The title card rises just as the surgery begins, and in a brief epilogue, we're transported to 221B Baker Street in London — the address of Holmes and Watson's residence in Doyle's series.
As rain falls, Watson arrives and checks the mail. Morstan opens the front door to greet him. "You're home early!" she says with a smile. He joins her inside, his "picture" of their lives having come true.
Butdidit come true? Or is it just a nice thought? His idea of heaven? That remains ambiguous.
Where can I watchWatson?
Watsonis available to stream on Paramount+.
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Watson wrapped its two-season run on May 3 after being canceled in early 2026. Key Points The final episode finds...
