The movie tells the story about a girl who has to hide and survive from a right wing terrorist while looking for her little sister during the terrorist attacks in Norway on the island Utøya, July 22nd.

Norway, 1204. A civil war between the birkebeiners —the king's men— and the baglers —supporters of the Norwegian aristocracy and the Church— ravages the country. Two men must protect a baby, the illegitimate son of King Håkon, who will be the future king and peacemaker, from those who want to kill him.

One Night in Oslo follows a group of young people in Oslo’s Eastern parts on the night before Norway’s National Day, and reflects their expectations and emotions ahead of the celebration.