But then the Skandians' most precious artifact the Andomal is stolen and the Herons, who were guarding it at the time, are shamed for their failure. To reprove their worth and regain their honor, they must track down the thief Zavac and his band of pirates and recover the artifact.
But it won't be easy. They must survive a frigid winter, cross stormy seas and battle deadly pirates.
Even with their training and the help of Skandia's greatest warrior they may not make it back alive...
After Hal and the Heron Brotherband flee Skandia, they end up in a sheltered bay named Shelter Bay. They spend a few nights sleeping on the boat, the Heron, while they create a shelter. The weather, which was horrible in the first place, worsens for several days. With nothing to do, the brotherband begins to fall apart. Stefan and Ulf argue about their sleeping spots in the shelter, and Hal ends up making them swap spots. Thorn berates Hal for neglecting the brotherband’s weapons skills, and soon after, Hal appoints Thorn as the trainer.
Thorn devises a series of exercises that perfect the brotherband’s various skills. One day, after Thorn gives the Herons a break from training, Hal and Ingvar reveal what they’ve been working on at night: a huge crossbow capable of shooting a 50-centimeter long bolt 300 meters. Hal says that when they get to the pirate Zavac, who has the Skandians' most prized artifact, the Andomal, in his possession, the crossbow will decimate them. Hal decides to mount the crossbow on the bow of the Heron, and the brotherband names the massive crossbow the Mangler.
Hal and the Heron brotherband set sail, as they need more supplies for the Mangler’s bolts. They head towards the nearby town of Skegall. They find out that Zavac’s ship, the Raven, has been sighted in the area. Thorn buys a new sheepskin vest because Hal used it for upgrading the Heron, and he points out that Hal now owes him quite a bit of money. They set off again. While Zavac is sailing around, he captures a trading ship. Zavac discovers emeralds in the ship and tortures the captain until he tells Zavac where he got the emeralds: a hidden mine in the town of Limmat. Zavac prepares to invade Limmat and get to their emerald mine by going to a Magyaran pirate meeting place and recruiting the crews of several other ships. Zavac deploys one of his captured trading ships, making it look like it’s sinking. The ship heads towards Limmat and they open up the gate for the ship. However, Zavac has stowed his pirate goons on the ship and they overrun the town. The crew of the Raven join in on the fight.
Meanwhile, Lydia, a 16-year-old from Limmat, is hunting in the forest with her atlatl, a tool that makes darts fly faster and a lot farther. She realizes that the town is being attacked, so she escapes with a borrowed skipper. Stig, Hal’s first mate, alerts Hal of a lone figure on a small figure waving to the Heron. The figure turns out to be Lydia, and Hal lets her stay aboard. She tells Hal about the location of the Raven, and Hal begins to sail towards Limmat in the hopes of catching Zavac and retrieving the Andomal.
Wolfwind, a Skandian wolfship, soon joins them. They sail to Limmat and meet up with the villagers who survived the invasion, who are hiding in the forest. Barat, their leader, immediately becomes super-overprotective of Lydia, who tells Hal and Stig that he’s been like that for ages, announcing that they’ll be married, etc. Lydia hates him for it. Hal hatches a plan to conquer the pirates. Using Wolfwind and the Heron, they’ll ferry the villagers over to the other side of the town under the cover of darkness. That way, the pirates will never expect them coming. Then, Hal will attack the watchtowers and the gate with the Mangler, burning them down with some bolts that he’ll set on fire. The pirates’ attention will be focused completely on the burning watchtowers and not the villagers, who will be slaughtering the pirates left and right.
Of course, Barat finds some way to argue with him. He says that the wind will be coming straight from the town, but Hal shrugs it off. The sail design on the Heron allows him to cut through wind like it’s no big deal. Meanwhile, Hal is racking his brain with ideas on how to get the gate to catch fire. It’s wooden, so it’ll burn eventually, but it might not catch anyway.
He decides that drenching it with oil is his best bet, but getting the oil there would be a problem. After a fitful night of sleep, Hal devises a plan. One night, while Stig is ferrying the villagers to the other side of town, Hal and Jesper are floating around on a log in the middle of the sea. They swim to the beach while looking like driftwood and Jesper uses his skills as a thief to sneak to the gate and hang a bladder of oil there. Stig picks them up right before they drown and they sail back. Soon, they mount an attack on the pirates. Hal and Ingvar work together to burn the watchtowers and the gate while Lydia picks off any archers that are getting too good with their bows. Barat leads the villagers, armed with an assortment of weapons, into Limmat and they take over the town. However, Zavac escapes before they can catch him.
Afterwards, a celebration is held. Barat claims to have created the plan to save Limmat, but Stig mutters to Hal that “All he did was sit around and argue.” When the Heron Brotherband leaves, Lydia decides to come with them because she really doesn't want to stay anywhere near the possessive Barat.