Have Dragon, Will Travel, Part 1

S3, E10: While gathering supplies, the riders hear of a rogue dragon rider attacking ships and stealing their provisions. They identify the rider's dragon with the Dragon Eye as a Razorwhip and pursue it to a remote island. One by one the riders are picked off by the rogue until Hiccup and Toothless chase her down and she reveals herself to be Heather, with her new dragon Windshear. The group mostly welcomes her back with open arms, but Hiccup is suspicious of her new, more aggressive behavior. Following her to Trader Johan's ship, Hiccup interrogates Johan and learns that Heather's island was attacked and her parents killed by Dagur, who she pursues for revenge while stealing supplies to help rebuild. Heather meanwhile tracks down Dagur alone but is captured by his new armada.