In an effort to recover from the distressing terms of Stoick's death, Toothless is faced with a series of events that profoundly confront and impact him, such as two Night Furies in far worse condition than him. But not the secretive and eccentric young male with afflictions, nor the female with a nightmarish past, could amount to an enemy threatening the genocide of Night Furies.

In Northern Alaska a terrible attempt on life has ensued, leaving a pup mentally scarred and alone. Sworn to rule over all else, the Revolution relentlessly pursue their goal and it seems they can't be stopped. Tired of it all, one wolf can lead the survivors to victory.