The Breakthrough ending explained - who is the killer in the Netflix drama?

Tense crime thriller The Breakthrough has been a surprise hit since it was added to Netflix, and viewers have been watching in droves - but who was the killer?

Netflix is the place to go if you're looking for true crime - the streamer has a plethora of documentaries and dramas dedicated to the criminal activities of humans. Woman of The Hour,  This is The Zodiac Speaking and Sweet Bobby have all attracted a host of viewers in recent months, and the latest crime drama to get everyone talking, is Scandi noir thriller, The Breakthrough. The series takes elements from a double murder that took place in in Linköping, Sweden, in 2004. It took 16 years for the case to be solved, and it was a genealogist who made the breakthrough. 

While the case is real, The Breakthrough is a fictional story about an unexpected hero, and unlikely collaboration in the hunt for the killer. The series also delves into how unsolved crime affects a society and what happens to people who are left without the answers they desperately need. If you're needing to know the answer to exactly who the killer was in the show, look no further.

The Breakthrough ending explained

In The Breakthrough finale, Per reveals he's found people who share genetic links with the killer. He needs swabs from a wider age range of the population to confirm his findings, and John tells him they can't just go out swabbing random people. The other police offer to get more volunteers to be swabbed, and Per even manages to get a swab from a journalist in return for giving a story. 

While this is going on, Per's daughter has run away from school again and he needs to leave the station to find out what's going on, despite John being reluctant for him to go. Per returns home and when he's gone, the old football coach arrives at the station to discuss the photofit of the killer, whom he suspects to be Andreas 'Ante' Persson. A photo he has with him of Ante from 2004 is compared with the photofit, and there are similarities.

Ante had been questioned at the time of the murders but refused to give a swab. However, as he's since been convicted of assault and he lived near the crime scene at the time of the murders, the police arrest him. Per thinks he may have found another relative that could be the killer, but John believes the arrest that's been made means this will be unnecessary. 

Everyone's suspicions turn out to be incorrect, when the swab results reveal the wrong man has been arrested. In a surprise twist, the journalist, Stina Eriksson, who agreed to give a swab in return for a story, is a close match to the DNA linked to the real killer. With this development, the suspects are clearly whittled down to two brothers, David Nilsson and Stefan Nilsson. Per calls John with the news and insists the murderer is one of the two brothers - and whoever it is also happens to be the cousin of the journalist.

When Per returns to the office, John is convinced David is the killer due to his loner nature, and wants him arrested the following morning. Neither Per or John can sleep that night, with Per worrying he might've made a mistake. Early the next morning, the John and the tactical team are waiting - they swoop in and David is taken to the station for a swab.

Who is the killer in The Breakthrough?

There is no twist - David is the perfect DNA match, and he's taken to the interview room where he confesses. David admits that he once killed two people on account of the voices in his head. After John and Per celebrate their victory, it's time to prepare to let the victims' families know the killer has finally been caught, and David's brother is also informed.  

Later, John and Per pay Adnan’s family a visit. They describe living in pain as a result of their loss, and how much the killer ruined their lives. Saad gives John Adnan’s watch, which he is initially reluctant to accept but does so in the end. Gunilla enters the room - she was named after the lady who tried to save Adnan at the time of the incident. 

John later meets with his son, Henry, and apologises for not being present for him, suggesting they start playing tennis together. Henry says he'd prefer scuba diving, and once they've agreed on a bonding activity, he congratulates his dad for solving the case.

As the finale comes to a close, Stina suggests to per that she'd like to write a book about his work on the case. As she shows him a photo of her with her cousin and the killer, David, together when they were children, Per agrees the book is a good idea.