What began as an unlikely friendship between an adolescent Viking and a fearsome Night Fury dragon has become an epic adventure spanning their lives. Welcome to the most astonishing chapter of one of the most beloved animated franchises in film history. Now chief and ruler of Berk alongside Astrid, Hiccup has created a gloriously chaotic dragon utopia. When the sudden appearance of a female Light Fury coincides with the darkest threat their village has ever faced, Hiccup and Toothless must leave the only home they've known and journey to a hidden world thought only to exist in myth. As their true destinies are revealed, dragon and rider will fight together to protect everything they've grown to treasure.

1809, France. Captain Neuville is called to the front, leaving his future bride heartbroken. Her sister decides to write letters on his behalf to cheer her up. But it all goes south when Neuville reappears.