A Low Key Wedding Brings 'Professor T's Season 4 Finale in for a Soft Landing

After the emotional gut punch of losing Lisa in Season 3’s finale, Professor T’s Season 4 conclusion, “The Warrior Gene,” does us all a solid in this turbulent year: it delivers a sweet, gentle story that feels like a hug from the show. Winters gets the emotional catharsis he so desperately needs; after some fretting, Zelda and Wilfred get married; and, following rom-com-style misunderstandings, Jasper and Dr. Goldberg take hesitant but definitive steps towards romance.

Wedding preparations are afoot as we begin the episode, with Wilfred and Jasper in their tuxes, complete with top hats. Dr. Goldberg happens by the shop window, and Jasper immediately worries she thinks he’s the one getting married. In classic fashion, the professor’s social graces make matters worse. He tries to clear things up by clarifying it’s his aunt who’s getting hitched, but bungles things further by not inviting her to the wedding. Jasper eventually realizes his mistake and invites her, but is it too late?

In another story branch we’ll later learn connects to the main tree, Ms. Snares’ friend Lyndon is lecturing on a new drug he’s developing, which may put Jasper out of a job. Initially uninterested, Jasper decides to attend after learning that Dr. Goldberg might be there. He listens skeptically while Lyndon touts “Topranitzol”: a drug that supposedly suppresses violence. This is clearly related to the “warrior gene” referenced in the previous episode. Lyndon’s drug targets the underdeveloped amygdala to eradicate violent behavior, but his talk of gene editing has weird eugenics vibes.

This week, Winters gets to be the one personally affected by a case. Not because he knows the victim, but because he witnesses Cambridge student Jay Morgan (Ludovic Lhoest) get hit by a car, and then the young man dies in Dan’s arms. We saw Jay stumbling as if drunk before wandering into the car’s path. As he’s trying to help Jay stay conscious, Winters involuntarily flashes back to Lisa dying. Then, a mystery: Jay’s last words are, “I killed him…I pushed him…”

Jay’s drug screen is clean, and no one’s been reported missing or assaulted. There was alcohol in Jay’s system, but nothing abnormal unless he had a low tolerance. One test suggests the use of diuretics, which are often used to mask steroids. Goswami tells him not to invent work, but Winters can’t let it go.

Without Goswami’s knowledge, Winters continues poking into Jay’s death, first speaking to his grieving mother, Viv (Laura Doddington), then to Jay’s rowing coach, Tina (Gemma Knight-Jones). Tina is offended and refuses to answer Winters’ questions, which only makes him more determined – especially after Highsmith finds Tina was fired from a previous position for encouraging performance-enhancing drugs.

Once she learns Highsmith got roped into helping, Goswami tries to make Winters realize his thinking is emotionally clouded. When she points out the similarities to Lisa’s death, he loses his temper and yells at his superior. He then heads straight to Dr. Goldberg for a session, acknowledging his mistake and loss of control. However, in the time it takes him to almost process healthy grief over Lisa, Goswami runs some tests based on Winters’ intuition and discovers he’s right: Jay’s cause of death is partly due to anti-coagulants added to steroids, which led to a brain hemorrhage. She gives her blessing to investigate.

The police bring Tina in, who swears she only gave her team natural supplements. Highsmith points out that two of the ingredients are diuretics used to mask steroids. The interview leads Winters and Highsmith to search for Alex Healy, the rowing captain who quit the team just days earlier but hasn’t been seen. They find Alex dead in the woods near his dorm, with empty beer cans nearby. There are unusual findings from Alex’s blood that match Jay’s results. Both students had compromised immune systems, leading Jay to become very drunk on a small amount of alcohol. Winters theorizes that Jay got too drunk and pushed Alex, who died from minor cuts since his blood also couldn’t clot. However, steroids are not the culprit.

It’s a good thing Jasper attended that lecture on Topranitzol, because conveniently, that’s the answer. He thinks Lyndon was testing his new drug on student volunteers and that it proved fatal: it comes with strict warnings not to mix with alcohol and has anti-coagulants. Under questioning, Lyndon is angry and insistent that he’s the victim.* Winters has a panic attack while trying to conduct the interview when he can’t stop seeing Jay dying in the street like Lisa. While Winters catches his breath, Jasper advises him to use the common ground of sudden loss to get through to Lyndon.

*(His car was just broken into, with his laptop and drug research stolen. Unclear if Jasper was responsible.)

When Winters returns to chat “informally” with Lyndon, he gets real and talks about Lisa, finally letting his guard down but still unable to speak her name. He knows that Lyndon’s brother died violently in an unprovoked attack, and reveals that Jay and Alex were the same age as Lyndon’s brother. Their families need answers. “We all need closure,” Dan stresses.

The police have evidence that Lyndon paid Jay and Alex for their participation; it’s basically game over for Lyndon. Winters agrees that Lyndon, who is near tears, is not a bad person. Then Lyndon says, “Say her name.” When Dan utters “Lisa,” it’s all over. The floodgates open, and Dan is sobbing. It’s precisely what he needed, and an essential reminder that grief must be realized for healing.

Moved by Dan’s raw vulnerability, Lyndon gives a full confession. He’s genuinely remorseful and begins with: “I wanted to make the world a safer place.”

But I promised you a wedding.  For all its suddenness, it almost doesn’t happen because Zelda feels selfish for disturbing her sister’s long-time companionship with Wilfred. It’s Jasper who convinces his aunt to act on love, and at the reception, Adelaide (via prerecorded video) blesses the union by revealing she was playing cupid all along.

The affair is small and elegant. The bride wears a smartly tailored ivory suit, while the groom looks smashing in his finery. During the ceremony, Zelda and Wilfred sit on chairs before a Justice of the Peace, exchange rings, and kiss sweetly. When she throws her bouquet, Ms. Snares catches it.

Inspired, it seems as if Jasper is going to make some kind of wild romantic gesture toward Dr. Goldberg. Instead, he has Lydia take him to the police fundraiser. Post-catharsis, Dan has also shown up, ready to play with the band in honor of Lisa. Surprisingly, Jasper is also there to play and takes his place at the drums. With Lydia’s encouragement, Jasper removes his gloves and leaves them off.

Back at the reception, Dr. Goldberg arrives. There’s some initial awkwardness, but she prompts Jasper to ask her to dance and insists he call her Helena. She’s delighted to notice his bare hands when they dance, and he declares he feels wonderful. All in all, it’s just a perfect ending to the hour.

• Can this be the tone of the show from now on?
• Though she’s late and nearly misses it, Highsmith manages to pass the detective exam.
• What does romance look like for Jasper – especially with someone who used to be his therapist?

All episodes of Professor T Season 4 are available for members to stream on PBS Passport, the PBS App, and the PBS Masterpiece Prime Video Channel, as are Seasons 1 through 3. Season 5 has already been greenlit and is expected to debut on Channel 4 in early 2026 before arriving on PBS later in the year.