Bilbo Baggins, the dwarves, and their leader Thorin Oakenshield, continue their quest to reclaim the Lonely Mountain and its treasure from the dragon Smaug. Guided by the wizard Gandalf the Grey, their journey leads them through treacherous lands swarming with orcs, deadly wargs, and giant spiders. As they press onward, the company meets the skin-changer Beorn and traverses the dark forest of Mirkwood, where they fall prisoner to woodland elves led by King Thranduil.

Separated from the dwarves, Bilbo must use his courage and wits to escape and help his friends. Meanwhile, Gandalf investigates the rise of a mysterious dark power in Dol Guldur. Uncovering an ancient evil, he realizes that their adventures are part of a much larger struggle against the resurfacing darkness that threatens all of Middle-earth.