The overarching villain was a minor character in Tolkien's novel, and when elevated to a main antagonist, he was somewhat ...

Smaug was the only great dragon alive in the Third Age ... Peter Jackson's The Lord of the Rings and The Hobbit trilogies.

Smaug was always going to be the foundation on which this movie -- and indeed ... Since it's an extended chase and battle with an awesome dragon, however, I didn't honestly mind lingering there ...

The party must complete the journey to Lonely Mountain and burglar Baggins must seek out the Secret Door that will give them access to the hoard of the dragon Smaug. And, where has Gandalf got off to?