The Gold of Valhalla by Martin Schmidt

3.20

Three siblings, Sofie, Jonas and Emma, move to Copenhagen when their father is appointed a job at the National Museum. One day, the ancient Norse gods, Loki, Thor and Heimdal, materialize to prevent the museum's legendary golden horns from falling into the wrong hands and threatening the human race with extinction. Because the divine powers of the gods aren't too efficient in a modern, hi-tech world, the kids step in and come to their rescue.