A nobleman and poet Ahmad ibn Fadlan, a subject of the Arab caliph, is sent on an assignment to a wealthy merchant. But events unfold so that Ahmad flees the caliphate and ends up in the North, captured by Scandinavian Vikings. At night, descendants of Neanderthals appear in the darkness—demons with bear heads and lion paws, attacking people, killing them, and eating the dead. A squad of Vikings sets out for the deadly battle against the tribe of the dead-eaters, led by the fearless Balivif (Beowulf). Ibn Fadlan became the thirteenth warrior in this squad who went out to fight the cave-dwelling tribe.