Christian (Robert Hansen) brings the unconscious Ask (Ralf J Hollander) to the surface

Then, one night, when Christian and Ask set off on a mission finally to find out what is really hidden inside the sub, they unleash the forces of a 60-year-old experiment in which Nazi doctors had used children to try to discover the secret of eternal life. The souls of the children are still trapped on board the sub, which begins to come slowly back to life. Ask is badly injured and Christian manages to get him back to shore, where he is rushed into intensive care. But he doesn’t respond to treatment: it is as if his soul, too, is trapped aboard U-461.
Christian finally persuades his grandfather that the only way to save Ask’s life is by freeing the trapped souls of the children and destroying all remnants of the experiment. Narrowly beating the other searchers - who turn out to be a sinister group of neo-Nazis - to the sub, Christian sets about fulfilling his task. It is a sequence which inevitably recalls the discovery of the Ark in Raiders, and it engenders the same kind of chills up and down the spine.
Featuring Robert Hansen - star of a romantic comedy called Kaerlighed ved forste hik (Love at First Hiccough), which screened successfully in Denmark this spring - in the role of Christian and newcomer Ralf J Hollander as Ask, the film is helped along by a carefully constructed script from Anders Thomas Jensen, who co-wrote both the Berlin Festival winner Mifune as well as this year’s Cannes entry The King Is Alive; and by the claustrophobic production design of Niels Sejer.
Although the work in the tank was “very demanding”, the most difficult scenes to film, says Obel, echoing the view of almost anyone who has shot scenes on and around small boats, were the scenes on the open sea. Swedish-born director Åke Sandgren - whose career began with a Golden Bear for Best Short in Berlin in 1984 and who has since included a couple of Best Swedish Film Awards - set out quite consciously to make a movie which functioned on at least a couple of levels: adventure... and then something more.
“Two ordinary Danish boys dive among flounders and floating seaweed,” he says. “On the sandy bottom they find something large and rusty that is bigger than their imaginations can comprehend and that shines more than all the gold treasures.”
But, he adds, “I did not want to make a film where the unlucky spirits are just ghosts or the Nazis just wicked men. Ask and Christian must be thinking persons in a story that shakes them existentially. I also think that 15 and 17-year-old youngsters explore moral questions and are interested in ethics.”