WARNING: The premise of this film contains unmarked spoilers for the story thus far.
Two hobbits, Sméagol and Déagol, were fishing in a river when the latter discovered a mysterious ring in the water. Upon seeing it, Sméagol killed his friend for the ring and retreated into the Misty Mountains. Over time, the ring’s power twisted his body and mind until he became a creature named Gollum. It was, in reality, the One Ring, an artifact forged by Sauron the Dark Lord in the Second Age of Arda in his campaign for world conquest. Many centuries have passed since that day. Gollum, having discovered that a hobbit named Frodo Baggins now bears the ring, will stop at nothing to retrieve it.
Meanwhile, Saruman, Sauron’s second-in-command has fallen, betrayed by his own servant, Gríma. At Isengard, Gandalf, Aragorn, Legolas, Gimli, and King Théoden reunite with Merry and Pippin. Gandalf retrieves Saruman’s palantír. Pippin looks into the stone as the wizard sleeps only to be telepathically assaulted by Sauron. Gandalf concludes that Sauron intends to attack Gondor in retaliation for his defeat at Helm’s Deep. Taking Pippin with him, Gandalf rides to Gondor’s capital city, Minas Tirith as his alliance prepares for one final battle against the forces of Mordor.