What is How to Train Your Dragon: Homecoming about?

It's been ten years since the dragons moved to the Hidden World, and even though Toothless doesn't live in New Berk anymore, Hiccup continues the holiday traditions he once shared with his best friend. But the Vikings of New Berk were beginning to forget about their friendship with dragons. Hiccup, Astrid, and Gobber know just what to do to keep the dragons in the villagers' hearts. And across the sea, the dragons have a plan of their own...