A mysterious girl, Heather, washes up on the shores of Berk. Proving herself a valuable addition to Berk, she wins the affection of everyone except Astrid, who notices Heather is particularly interested in flying dragons and in the Book of Dragons. Hiccup refuses to believe she could be lying about anything, but when Heather disappears on Stormfly, headed for Outcast Island, Hiccup and the village realize they were duped.