Episode Title:Crushing It.Episode Description:The riders are tracking down an elusive Rumblehorn that is going around their island base scaring all the dragons away. At the same time, Gobber appears and warns Hiccup of an unpleasant change in Stoick back on Berk that is currently driving everyone crazy. Hiccup enlists the aid of his father in tracking down the Rumblehorn, but Stoick comes to question its intentions upon discovering it. They eventually learn the Rumblehorn has been attempting to warn everyone of an approaching tsunami and chase them off before the wave would wipe them all out. With the aid of Stoick and the Rumblehorn, the riders create a wall to block the wave and protect the island. In the end, it is revealed that Stoick missed Thornado but in turn comes to bond with the Rumblehorn, who becomes his new dragon Skullcrusher.