Vig Hakanson time-travels into the body of a fifteen-year-old boy in ninth-century Scandinavia. His sister, who raised him, moves to Britain with her second husband, leaving him a farm north of Gothenburg. A storm destroyed his crops the previous year, forcing him to sell his livestock. This year’s harvest yields only four hundred kilograms of barley; after setting aside ten kilograms per mu for seed and paying around forty kilograms as taxes, he has two hundred kilograms left, barely enough to avoid starvation. He laments his fate, wishing he had traveled to the Tang Dynasty or Byzantium instead of this harsh northern land. One morning, ravens circle overhead and he hears a scream from his neighbor Joren’s house. Eight raiders are looting. He joins twelve men to form a shield wall, with women and boys on the flanks using hunting bows. They advance; a woman hits a raider but is killed by an enemy arrow. At thirty meters they halt and shout; the outnumbered raiders flee, two shot dead in the back. Vig feels his heart pound but suppresses fear. Afterwards, he packs his best grain and walks twenty kilometers south to Gothenburg to pay taxes. The settlement has seven hundred residents. In the market, he sees Slavs selling honey wine, a blacksmith hammering iron, and a Sami witch painting on birch bark. He then encounters a group of noisy Vikings singing songs of Odin. Their leader, a bearded man, hands him a large lamb chop and offers him mead. Vig is stunned to realize he has met Ragnar Lothbrok, the legendary pirate who once sacked Paris. That evening, Ragnar and his men are invited to Lord Olaf’s longhouse. A dispute erupts over the division of plunder; Ragnar leaves in anger. Olaf then orders forty shield-bearers to ambush him. Vig, working at a neighbor’s house, watches through a gap as Ragnar and fifteen comrades form a wedge formation and charge into the enemy. Ragnar cuts down four shield-bearers, including one whose left hand he severs, and chases Olaf, who flees into the house where Vig is hidden. Olaf pins Ragnar down and reaches for his dagger. Vig instinctively grabs a burning log from the fire pit and throws it at Olaf, then severs his wrist with his hand axe and buries the axe deep in Olaf’s skull, killing him. Vig helps Ragnar to his feet, saying it is repayment for the meal. With Olaf dead, the remaining shield-bearers lay down arms. A comrade proposes Ragnar as the new Jarl. The seven hundred residents gather; Ragnar promises a two-year tax reduction, and they accept his rule. In the longhouse, Ragnar allows his followers to take spoils. While others grab swords, chainmail, and silver, Vig searches for the five sheepskin scrolls that show the locations of all farmland, used for tax collection. He realizes they are crucial for ruling. But they are missing: Olaf’s wife and children fled during the night with the scrolls. This threatens Ragnar’s ability to collect taxes. Ragnar summons his wife Ragnheid, a renowned shield-maiden, who arrives with twenty shield-maidens and their youngest son Halfdan. His old friend Gunnar brings more warriors, swelling the garrison to sixty. Vig begins combat training under Ivar the Boneless, Ragnar’s eldest son. Ragnar himself teaches him five essential sword techniques: overhead chop, counterattack, thrust, blade entanglement, and disarm. He advises Vig not to over-rely on his shield, to let the enemy attack and then exploit the opening, and to watch the enemy’s pace for feints. Vig practices daily, gaining strength and skill, until he can exchange blows with Ivar. By winter, he is a competent shield-bearer. Food supplies dwindle, so Ragnar orders the construction of longships for a spring raid. Carpenters build three warships in a month, using oak planks, iron nails, and tar-soaked moss to seal gaps; the sails are wool coated with beeswax. In late February, the fleet is ready. An envoy from King Eric of Oslo invites Ragnar to a council. Sailing north, Vig is amazed by the hundreds of longships in Oslo fjord. At the meeting, nine nobles sit in a circle. Eric proposes a massive attack on Londinium in Essex, praising its wealth, and asks Ragnar to lead the fleet because of his eighteen years of raiding experience. A noble scoffs at Ragnar’s common birth, saying he is not equal to the jarls. Ivar, enraged, challenges the noble to a duel under the eyes of the gods. The noble declares Ivar unworthy and sends a shield-bearer to fight in his place. The shield-bearer steps forward, and the story builds to this duel as the expedition to Londinium is being prepared.