To coincide with the launch of the full series on All 4 from Friday 24 June, the first episode transmits on Channel 4.
Walter Presents - which showcases the best foreign language drama series from around the world - continues with this chilling Norwegian psychological thriller.
Max Sorensen has transferred to a new police department in Olso, after an extended period of leave following his son's death. He teams up with Sander Holm, an older detective with more experience in the city and a difficult home life.
On their first day together, they are sent to an inexplicable case: four teenage boys have been found dead in a privately owned but abandoned pool. Forensics say that all the evidence points to the boys having drowned, but there was no water in the pool.
When Sander and Max check the water tanks, live eels slide out onto the floor. Max is baffled and uneasy about the case, but Sander has ready-made theories for the occurrences based on his experience of dealing with drugs and gangs.
Both troubled men are about to find out that nothing about this case is straightforward and nightmares can invade waking life.
Starring Anders Danielsen Lie, Anders Baasmo, Selome Emnetu, Marius Kolbenstvedt, Nina Ellen Odegard, Heidi Goldmann, Kaveh Tehrani and Torgny Amdam. In Norwegian with English subtitles.