Episode Title:Between a Rock and a Hard Place.Episode Description:The riders ambush a hunter convoy only to find it loaded with marble blocks and split into teams to investigate. Hiccup, Fishlegs, and the twins comes across a marble mining operation on a nearby island using trained Catastrophic Quakens, and while Fishlegs is determined to save them, Hiccup fears it may already be too late. Meanwhile, Astrid, Heather, and Snotlout find the marble is being used to construct a dragon-proof fortress that will make it impossible for any captured dragons to escape. Fishlegs manages to free the Quakens just as their poundings cause the island to sink and have them destroy the Hunters' stone base. The riders fear how many other slave dragons the hunters have while Viggo assures the riders will pay.