The film continues the journey of Bilbo Baggins, the Wizard Gandalf, and thirteen Dwarves led by Thorin Oakenshield as they journey to reclaim the Lonely Mountain from the dragon Smaug.

As their quest progresses eastward, they face the skin-changer Beorn and a swarm of giant spiders in the treacherous forest of Mirkwood. After escaping capture by the dangerous Wood-elves, the company travels to Lake-town and eventually reaches the Lonely Mountain. There, Bilbo must confront the ultimate danger—the massive, fire-breathing dragon Smaug, who guards the lost treasure of Erebor. Meanwhile, Gandalf investigates a growing evil at the ancient fortress of Dol Guldur, discovering the terrifying return of the Necromancer.