Dept Q: Netflix's hit show's ending explained

Carl, Akram and Rose discover that Merritt's lover Sam Haig, who was killed in a climbing 'accident', was actually an impostor, after the same person appeared to be in two places at once.

They realise that Sam's time spent in juvenile detention coincides with Lyle Jennings, the brother of Harry Jennings who had dated Merritt as teenagers, before trying to burgle their house and giving her brother William permanent brain damage.

However, it is revealed that Harry had only snuck into their house to take a beloved necklace for Merritt, and had never hurt William, but it was actually Lyle who followed Harry to Merritt's house and attacked William, supposedly to defend his brother.

In flashbacks, it is revealed that Lyle - who bears a resemblance to Sam Haig - kills Sam in order to assume his identity, which is when he begins meeting with Merritt in order to get close to her, eventually kidnapping her from the ferry and placing her in the same chamber which his mother would abuse him and Harry in as children.

The trio realise that Lyle is directly involved in Merritt's disappearance, and visit his parents' property. There, they discover the police car and body of the original officer assigned to the case, and finally discover Merritt, who is dying in a chamber slowly growing in pressure.

After being attacked by Lyle, Akram kills him while Morck is shot in the shoulder. They manage to save Merritt, who is taken away in a portable hyperbaric chamber and reunited with her brother. Meanwhile, Lyle's mother Ailsa, who also kidnapped Merritt, tries to escape and dies by suicide after being met at the ferry by police.

Clearly the mystery of who shot Carl, James and PC Anderson will be going into season two, but some headway was made into the investigation in season one. Firstly, a theory is formed where it is apparent that two people were involved in the shooting - and that one was hiding in the flat before Carl and James arrived, while another was waiting in a car.

Secondly, PC Anderson was more involved in the case than they originally believed, as he graduated at the top of his class from the police academy, but Carl recalled him making simple mistakes in the flat, hinting that he was acting that way on purpose.

It is also recalled that PC Anderson claimed to have discovered a body at the apartment after receiving a report from the daughter of the victim - who turns out not to exist. As such, it appears that Anderson was lured to the crime scene - and Carl and James weren't supposed to be there, but made a surprise stop after just passing by.

With a successful investigation under their belt, Carl's team remains in commission, with Rose and Akram settling down with all of the boxes of missing person's files, ready to help select their next case.

Thanks to Carl knowing about Stephen Burns' involvement in ensuring that Graham Finch would be released from prison, he also arranges some reassurances about the continuation of his team, and making Akram an official member of the police so that they continue their work.

After plenty of back-and-forth, it appears that Carl's very tentative romance with Dr Rachel Irving is set to continue after she visits him in his home and makes friends with his stepson Jasper and his lodger. We can't wait to see more of her!