Vancouver author Cynthia Heinrichs’ second book is a radical departure from her picture-book debut, Mermaids. Using Norse sagas, runes carved on an ancient Orkney tomb, and generous doses of imagination, Heinrichs has crafted a long, complex story that is part historical fiction, part mystery, and part fantasy.

In the winter of 1153, young Malcolm is sent north by his father to help Earl Harald regain his kingdom in the Orkney Isles. He travels with a mixed bunch of Norsemen and Scots who, when not laughing at Malcolm, spend their time eating, drinking, fighting, and telling stories.

As they head north, Malcolm overhears a conversation that convinces him there are plots afoot and a spy in their ranks. After a blizzard traps some of the men in an ancient burial mound (a detail rooted in Orkney legend), the tension escalates and Malcolm is troubled by strange dreams. In one, the old Norse gods come alive, undermining Malcolm’s Christian beliefs and showing him that he is a receptacle for ancient powers.

Under the Mound is an exciting book, but it tries to be too many things. Odin and the other Norse spirits are very real; they tip the book into fantasy when its strength is its basis in history. And Malcolm starts out a bit too modern, naive, and sensitive for a 15-year-old coming of age in the harsh 12th century.

Despite the help offered by a character list at the beginning, the tale is convoluted, and Malcolm’s confusion at what is happening to him is sometimes mirrored in the reader. A slow start will also likely make this a tough go for younger teens without a solid background or interest in Norse mythology and Orkney archaeology.