A young Norwegian boy in 1850s England goes to work as a cabin boy and discovers some of his shipmates are actually pirates.

Haakon Haakonsen didn't want to go to sea so young, but when his father, a Norwegian sailor, comes home with a badly wounded foot in the 1850s, the Haakonsen family finances require him to enlist as ship boy aboard a British ship under Royal Navy authority. After some hazing he buckles up to learn the hard work and gets accepted by the rough crew. Then Royal Navy lieutenant John Merrick is welcomed to take charge of security on a long voyage to Sidney and Calcutta, through pirates-infested waters, but Haakon distrusts him after finding out that he packed concealed weapons; indeed Merrick secretly poisons the captain. Haakon and his guardian angel, his father's best mate Jens, were about to feel the claw of the cat for helping a stowaway when a rock wrecks the ship. Haakon washes up an island where he finds a pirates treasure and weapons.—KGF Vissers

[Spoilers] From the novel by O.V. Falck-Ytter titled "Häkon Häkonson, a Norse Robinson Crusoe", a 13-year-old Norwegian boy (Smian Smestad) is obliged to go sea in 1859 as a cabin boy in order to support his family, who are in humiliating financial straits. Fortunately, he ships with his father's good friend Jens (Trond Peter Stamsø Munch), who introduces him to ship life. Haakon's problems begin when he discovers but does not report young stowaway Mary (Louisa Haigh), then involves Jens in the crime. Meanwhile, the ship has become secretly infiltrated with pirates, and as tension around the crime mounts, a storm causes the ship to founder and all aboard are thrown upon their own resources. Haakon awakens alone on the beach of a jungle island of singular beauty, where he finds the recent remains of pirates, including their enormous treasure and proof that an impostor aboard his ship was one of them, the notorious Merrick (Gabriel Byrne). Stranded alone, he experiences elation and melancholy as he explores the island learning its secrets and making it his new home, all the while trying to devise a means of escape. After a number of months, he discovers Jens and Mary, and together they begin to settle into island life as Mary and Haakon quickly become devoted to each other. But a cohort of the pirates has survived as well, including Merrick, who, as Haakon has anticipated, returns to recover his treasure. Chases, rescues, and battles ensue across the island, more merry than sinister until, with his friends' help, Haakon prevails through cleverness and heroism. In perhaps the most touching moment of the film, he returns home to his parents in Norway immensely wealthy and in a position to shame all those who humiliated his family when they were poor. He introduces them to Mary and says she "will be staying with us for a while."—Jasha