Basil spends the whole show being asked to be someone he isn’t. By the end, that gap between the actor and the character he played becomes the very thing that lets him see what nobody else in the hotel could. The twist isn’t just about who did it. It’s about how a man trained to fake being clever finally has to actually be clever, and what he chooses to do once he is.
Here’s the full ending broken down, plus a few of my own theories on the parts the show leaves quietly unresolved.
Quick Facts
- Title: The Final Problem (El problema final)
- Platform: Netflix, streaming from September 25, 2026
- Based on: Arturo Pérez-Reverte’s 2023 novel of the same name
- Director: Félix Viscarret
- Episodes: 4, roughly 50 minutes each
- Setting: A remote hotel on an islet near Mallorca, called Santa Agueda, in 1959
- Cast: José Coronado (Basil), Martiño Rivas (Francisco Foxá), Maribel Verdú (Mrs. Raquel Ausländer), María Valverde (Adela Figueroa), José Condessa (Tony), Cristina Kovani (Vicky), Pepón Nieto (Doctor Seruya), Gonzalo de Castro (Fonseca), Yaiza Guimerá (Frau Klemmer)
Quick Recap: What Happens
- Thirteen people get stranded at a hotel on the islet of Santa Agueda after a storm cuts off the radio and any way to leave.
- A guest known as Elisa Mander is found dead, first assumed to be suicide.
- Basil, a retired actor famous for playing Sherlock Holmes, starts suspecting murder and begins investigating with crime writer Francisco Foxá.
- A second body turns up: Doctor Seruya, who had gotten too close to the truth.
- A German tourist, Mr. Klemmer, is also found dead, with a torn scrap of a magazine clenched in his fist.
- Basil eventually realizes the woman he knew as “Adela Figueroa” is actually Elisa, and the real Adela was the one who died first.
- Elisa’s real motive was revenge against Klemmer, a former SS officer tied to her husband’s death during the war.
- Basil, who has his own guilty history with Elisa, chooses to help her get away rather than turn her in.
The Full Breakdown
The Body Everyone Misidentified
The central trick of The Final Problem is simple once you see it, and genuinely clever before you do: two women swapped names before either of them died. The woman everyone calls Adela throughout most of the investigation is really Elisa. The woman who actually died that first night, the one the hotel spent the whole show calling “Elisa,” was really Adela.
Basil, Foxá and the rest of the hotel guests spend the investigation asking the wrong question. They keep asking who could have killed Elisa Mander. The real question was always who Elisa Mander actually was.
Why Elisa Wanted to Become Adela
Elisa didn’t have Adela’s money, her social standing, or the easy freedom that comes with both. Adela could do more or less whatever she wanted without consequence. Elisa had spent her life struggling for everything, and Adela, according to multiple accounts of the story, treated her with a kind of casual condescension that only deepened Elisa’s resentment over time.
So when the opportunity arose to trade places, Elisa took it. Becoming Adela meant escaping her own life entirely: the poverty, the powerlessness, and the years of being looked down on by someone who had never had to work for anything. But jealousy over Adela’s lifestyle wasn’t the only motive, and honestly, I don’t think it was even the main one.
The Real Target Was Klemmer
The bigger, darker reason Elisa came to Santa Agueda was to kill Mr. Klemmer, a German tourist staying at the same hotel. Klemmer was a former SS officer connected to the death of Elisa’s husband during the war. Her husband, a pilot, had been shot down and taken prisoner. When he tried to escape a POW camp along with several other men, a German squadron captured them and had them executed by firing squad. The order for that execution had been signed by Klemmer himself.
After the war, Klemmer avoided any real punishment. He spent only a short stretch in a prisoner-of-war camp before going on to live comfortably, seemingly untouched by what he’d done. When word eventually reached Elisa that he was still alive and well, she began planning her revenge, and the trip to Santa Agueda, along with the identity swap, was built specifically around that plan.
In other words, Elisa’s whole scheme was designed to solve two problems at once: escape the life she hated by becoming Adela, and finally make Klemmer answer for what he did, all while staying completely unrecognizable while she did it.
How the Murders Unfolded
Once Elisa killed the real Adela, she had effectively erased her old identity and stepped fully into a life that wasn’t rightfully hers. But covering that up meant more people had to die.
Doctor Seruya started noticing details that didn’t add up about the woman claiming to be Adela, and Elisa killed him to protect her secret. Then came Klemmer himself, the man she’d come to the island to kill all along. Elisa left a small torn fragment of a Paris Match magazine article somewhere Klemmer would find it, an article connected to his own wartime trial. Curious and clearly nervous about what it might mean, Klemmer went to investigate on his own, unaccompanied, straight into Elisa’s trap.
How Basil Actually Solved It
This is where the show’s central idea, an actor who played a detective now having to actually detect, pays off. Basil found the magazine fragment clenched in Klemmer’s fist and recognized where it had come from. From there, he started connecting Klemmer’s wartime past to what he already knew about Elisa’s husband.
But the piece that cracked the whole case open was physical evidence, not just deduction. Basil dug into old records and found Elisa’s identification from her RAF days, back when she still had dark hair. He’d also been quietly studying the hands of the woman claiming to be Adela throughout the investigation, and once he lined up that memory against the ID photo, the disguise fell apart. The woman who’d been walking around the hotel as “Adela” for days was Elisa Mander, alive the entire time.
Basil and Elisa’s Shared Past
The reveal hits differently because Basil isn’t a neutral outside investigator here. Years before the events on Santa Agueda, Basil and Elisa had a personal history. They met at one of his celebratory parties, back when she was a young woman with dreams of becoming an actress. Basil encouraged those dreams, even promised to help arrange an audition for her, and then abandoned her once he’d gotten what he wanted from the situation.
Elisa never forgot it. Basil, by his own admission, nearly had.
When he finally puts together that the woman he’s been investigating is the same person he once used and discarded, it changes the entire shape of his decision. He isn’t just solving a mystery anymore. He’s confronting a mistake from his own past that helped shape the person standing in front of him.
Why Basil Lets Her Go
Rather than handing Elisa over once the truth comes out, Basil chooses to help her escape in the final episode. It’s not a clean, heroic decision, and the show doesn’t pretend it is. He knows exactly what she did. He knows she killed Adela, Seruya and Klemmer, three people, one of whom was, sure, a war criminal, but the other two were not.
But he also can’t separate her actions from what he did to her years earlier, or from the decades she spent being underestimated, used and looked down on by people who had more power than she did. Letting her go isn’t forgiveness for the murders. It’s Basil accepting a debt he owes her that he can never fully repay, and choosing to pay a small, imperfect part of it anyway.
What This Ending Actually Means
I think the show is using its Sherlock Holmes framing as a genuine thematic argument, not just a fun premise. Basil spent years pretending to be a man who solves crimes through pure logic and detachment. Elisa spent years pretending to be a woman she wasn’t, purely to survive a world that had already used her up once. Both of them built an entire identity around a performance other people believed in completely.
The difference is that Basil’s performance made him famous and comfortable. Elisa’s performance made her a killer. That contrast, I think, is the real “final problem” the title is pointing at: not who committed the murders, but what happens when the roles people force you into, actress, assistant, damsel, footnote in a famous man’s story, finally run out of room, and there’s nothing left to do but take one by force.
My own theory on this: I don’t think the show frames Elisa as purely a victim, and I don’t think it wants us to either. It deliberately keeps her jealousy of Adela’s wealth right alongside her legitimate war-crime revenge motive, refusing to let one excuse the other. That’s a genuinely uncomfortable choice, and I think it’s the smartest thing the ending does. It asks you to hold sympathy and condemnation for the same person at the same time, rather than letting you pick a side and settle in.
A Quick Word of Caution on the Details
Different recaps of this ending use slightly different names for a couple of secondary characters, likely due to dubbing or translation variations, so if you watch and hear a name that doesn’t quite match what you’ve read elsewhere, that’s probably why, not a mistake on your part.
Final Thought
The ending doesn’t give Basil a triumphant final scene as the detective who cracked the case. It gives him a quieter, sadder one: a man who spent his career pretending to have all the answers, finally getting a real one, and choosing not to use it the way anyone expected him to.
Your turn: Do you think Basil made the right call letting Elisa go, or did solving the mystery mean nothing if he wasn’t going to act on it? Let me know in the comments, and catch The Final Problem streaming now on Netflix.