A saw, body parts, a suitcase that is almost impossible to carry - the first few minutes of "Gefesselt" make it clear to viewers that this series is not going to be a walk in the park. And at the centre of it all is lead actor Oliver Masucci, who is guarding a dark secret as the eccentric but charming furrier Raik Doormann: In a self-built and soundproofed nuclear bunker under his house, he tortures and kills women from his personal circle without anyone realising it. Even his family is unsuspecting.

The plot is inspired by the legendary criminal case of the so-called "acid barrel murderer", one of Germany's most notorious serial killers who wreaked havoc in Hamburg in the 80s and 90s. The team behind the series became aware of the real case through policewoman Marianne Atzeroth-Freier. "She was the one who recognised the murder case in the first place. She was one of the first women in the Hamburg homicide squad to bring down the perpetrator because she listened to the victims and their relatives and investigated against the resistance of her male colleagues. Without her, the missing women would never have been found," reveals Executive Producer Dietmar Güntsche, who realised the series together with the two producers Nadine Grünsteidel and Ulrike Schölles with his company Neue Bioskop Television.

When it finally became clear that Neue Bioskop would realise the project in collaboration with Amazon Prime Video in a 6x45 minute format, the film team had to pore over police files and talk to people who were involved in the case at the time. "We really had a lot of material - you have to condense it, especially to give yourself creative freedom. We wanted to capture the spirit of the story and still tell it in a modern way," explains Director Florian Schwarz. "To this day, nobody knows what really happened in the bunker. Fortunately. Because that's where you start to develop stories." Even though the series is based on a true criminal case, it mixes true crime with fiction. Names and events were also changed for the series.

Filming took place all over Germany in 2021: For example, Raik Doormann's house and the square in front of it were filmed in Hamburg. The neighbourhood pub Haifisch Bar also makes an appearance in the series. The police station, on the other hand, from which investigator Nela Langenbeck (played by Angelina Häntsch) gradually uncovers the crimes of the acid barrel murderer, was filmed in Munich. Doormann's nuclear bunker, on the other hand, is located in Leipzig. Filming took a total of 67 days, around four weeks of which the crew spent travelling in Hamburg.

67 days centred on the deeds of an alleged serial killer - does that ever get to you? "Fortunately not so much," emphasises Florian Schwarz. "Even though I've always had a soft spot for dark stories and can handle them well, it was something else here - precisely because "Gefesselt" is based on a historical case with real victims and traumatised relatives. In contrast to a completely fictionalised story, the inner distance is less. That exhausted us after three months of filming.

He drew inspiration from films with similar themes, such as "Manhunter", "Gerald Kargel's "Angst", the series "American Crime Story", or, with regard to the treatment of depictions of violence, Fatih Akin's "The Golden Glove".

In addition to the extensive research into the criminal case, the set design was another challenge - because the entire series is set in the 80s and 90s. "We worked intensively on the set design six months before filming began and studied a lot of historical material such as chronicles, police photos, films, of course, but also furniture catalogues from the time with our production designer Johannes Salat," says Florian Schwarz. They were also inspired by the photography of the time and the brown-tinged images, as a look into Raik Doormann's flat directly proves.

But what use is the best set design if the acting is not convincing? Angelina Häntsch is more than convincing in her role as policewoman Nela Langenbeck, who has to fight for her convictions in a man's world and thus bring the pieces of the puzzle together. "It's absolutely fascinating how she brings her character to life, who has to deal with the case on various levels," says Florian Schwarz. In Oliver Masucci, the "Gefesselt" team has brought one of the most intense and versatile actors of recent years on board. "Oliver Masucci is a thoroughbred actor who stays in character even during breaks in filming and delivers an uncanny and expansive performance," says Executive Producer Dietmar Güntsche. And Florian Schwarz adds: "He's simply not afraid to delve into human abysses, you have to have the courage to do that."

The first two episodes will premiere at Filmfest Hamburg on 1 October - the series is set to launch on Prime Video in January 2023. On Friday the 13th, there's not really much more to say than: Lights out, scary on.