Episode 4 of "The Breakthrough" kicks off with Per in dire need of expanding the database to definitively pinpoint the murderer's lineage. Driven by desperation, the police team and their circle of contacts readily volunteer for DNA swabbing. A nosy reporter starts probing around, prompting Stina to preemptively strike. She leverages a past favor to secure an exclusive interview with Per. Though he initially balks at the timing, he relents on the condition that she submits a swab, which she promptly does. Meanwhile, Klara flees once more, leaving the team in disarray. John, seeing the strain, concedes and urges Per to prioritize his family by working from home, a suggestion he readily adopts.
But how will Per unravel the killer's identity? The coach, burdened by guilt for his delay, finally opens up. He confesses his reluctance to believe the killer could be Ante. Francy recalls interrogating Ante, who declined the swab test – a common stance back then since it was voluntary. His prior assault charge and proximity to the crime scene only heighten suspicions. These details suffice for the officers to apprehend Ante.
While Per narrows his search perimeter to Algbosatter, John interrupts with news about Ante. However, Ante's DNA doesn't match. The hunt resumes as Francy transmits fresh swab results to Per. Stunned, Per repeatedly cross-checks his meticulously crafted family tree. Each time, the results astonish him: Stina's identical cousins, David and Stefan Nilsson, emerge as the closest matches.
Empowered by this revelation, John secures an arrest warrant. Stefan, gainfully employed and with a family, contrasts sharply with David, mentally unstable and living in solitary confinement. The judge grants the warrant, authorizing a tactical team's deployment.
How does everyone react to the arrest?
Of course, Stina finds out about the tactical unit. She insists on intel and threatens to talk about the case online. Not wanting David to get a heads-up, John tells her she is the missing piece.
That evening, Per and John separately show up at the crime scene. Per is worried he may be wrong and John tells him not to worry.
It is past 6 am and the squad is one edge. David’s arrest is smooth and they do a swab. While they wait for the results, the cops recall how David had refused to do a swab back in 2004. It is a match and everyone is relieved. During the interrogation, David confesses that he killed Adnan and Gunilla as the voice in his head told him to kill two people to find peace. The cops gather that he is a recluse and he only ever spoke to his brother.
The cops alert Stefan who tears up as he is shocked. John tells Gunilla’s husband who reveals he dreamt of her that same morning. Next, Adnan’s family is informed. Saad thanks John for keeping his promise and gives him Adnan’s watch. They introduce their youngest daughter, Gunilla.
Per wonders what happens next and John decides to patch up with his son. He apologises and wishes to be in his life. Henry agrees, congratulating him on the case which has John delighted.
At the end of The Breakthrough Episode 4, we see that Per’s lectures are a hit. Klara helps him and one day, Stina visits. She shares a photo of her and David and wonders what went wrong with him. She wants to write a book on genealogy and Per agrees to join her.
Is "The Breakthrough," also known as "Genombrottet," rooted in factual events? Indeed, it is. This dramatic narrative unfolds from the pages of a non-fiction tome titled "Genombrottet," authored by Anna Bodin and Peter Sjolund, whose lives served as the inspiration for the characters Stina and Per.
In the chill of October 2004, the tranquil town of Linkoping was shattered by a gruesome act: Daniel Nyqvist brutally murdered Mohamed Ammouri and Anna-Lena Svensson with a knife, his blood left incriminatingly on the blade as he discarded his beanie at the crime scene. Despite the diligent efforts of law enforcement, who conducted an exhaustive 5,000 DNA tests, the perpetrator remained a shadowy figure.
Years passed—first, in 2010, a composite sketch of the suspected killer emerged, followed by a second iteration in 2018, crafted from his DNA profile. Then, in 2020, two years after the apprehension of the infamous Golden State Killer, the case witnessed a pivotal moment. The police secured a breakthrough by enlisting the expertise of Sjolund, who utilized cutting-edge genealogy mapping to trace the killer's DNA back to its origins, uncovering his bloodline. Initially, suspicion fell on Daniel's brother, but he was soon cleared. The definitive proof came when Daniel's DNA matched the hair found in the abandoned beanie, leading to his confession—a confession echoing the motive portrayed by David in the show.
Condemned for two counts of murder, Daniel faced justice, though his punishment was unconventional: psychiatric care and financial compensation to Ammouri's family and the state. Svensson's kin, however, declined any monetary settlement. In a poignant gesture of gratitude, Ammouri's youngest daughter bears the name of the second victim.
