The second book in the How to Train Your Dragon series.
 
When a huge, six-and-a-half-foot floating coffin with the words BEWARE! DO NOT OPEN THIS COFFIN arrives, can you guess what happens next?The Quest to discover the treasure of Hiccup's ancestors begins and Hiccup needs to find it before Alvin the Treacherous gets his hands on it.

But when a dragon called the Monstrous Strangulator is thrown into the mix, things are about to get seriously SCARY.