In August 2017, Jens Moller, chief of homicide in Copenhagen, learns of a missing Swedish journalist who has not returned from interviewing the designer of a homemade submarine.

As the police incident room is flooded with calls regarding the case, Jens and his team follow up various leads.

With the volunteers and divers continuing their search for evidence, Jens explains to Jakob that it is very difficult without the exact trace of the route taken by the submarine.

Prompted by Joachim, Jens asks the Swedish police to borrow their cadaver dogs, not commonly used in Denmark.

Even with the tremendous finds of the divers, Jakob admits that there is still too little evidence to charge the suspect with murder.

The team remain focused on being able to establish the guilt of their suspect, as Jakob reminds them that the benefit of doubt lies with the accused.