The Lord of the Rings

Early in the Second Age of Middle-earth, elven smiths forge nine Rings of Power for mortal men, seven for the Dwarf-Lords, and three for the Elf-Kings. Soon after, the Dark Lord Sauron makes the One Ring, and uses it to attempt to conquer Middle-earth. Following the Last Alliance of Elves and Men's fall, the Ring is seized by Prince Isildur; and after Isildur was killed by orcs, the Ring lies at the bottom of the river Anduin for over 2500 years. Over time, Sauron captures the Nine Rings and creates the Ringwraiths. The One Ring is discovered by DÃ©agol, whose friend, SmÃ©agol, kills him and takes the Ring for himself. The Ring twists his body and mind, and he becomes the creature Gollum (Peter Woodthorpe). Hundreds of years later, Bilbo Baggins (Norman Bird) finds the Ring in Gollum's cave and takes it back to the Shire.
Years later, during Bilbo's birthday celebration, the wizard Gandalf (William Squire) tells him to leave the Ring for his relative Frodo (Christopher Guard). Bilbo reluctantly agrees, and leaves the Shire. Seventeen years pass, during which Gandalf learns that evil forces have discovered that the Ring is in the possession of a Baggins. Gandalf meets with Frodo to explain the Ring's history and the danger it poses; and Frodo leaves his home, taking the Ring with him. He is accompanied by three hobbit friends, Pippin (Dominic Guard), Merry (Simon Chandler), and Sam (Michael Scholes). After a narrow escape from the Ringwraiths, the hobbits eventually come to Bree, from which Aragorn (John Hurt) leads them to Rivendell. Frodo is stabbed atop Weathertop mountain by the chief of the Ringwraiths, and becomes sickened as the journey progresses. The Ringwraiths catch up with them shortly after they meet the elf Legolas (Anthony Daniels); and at a standoff at the ford of Rivendell, the Ringwraiths are swept away by the river.
At Rivendell, Frodo is healed by Elrond (AndrÃ© Morell). He meets Gandalf again, after the latter escapes Saruman (Fraser Kerr), who plans to ally with Sauron but also wants the Ring for himself. At a council, Bilbo, Gandalf, and others debate the One Ring, and Frodo volunteers to go to Mordor, where the Ring can be destroyed. Thereafter Frodo sets off from Rivendell with eight companions: Gandalf; Aragorn; Boromir (Michael Graham Cox), son of the Steward of Gondor; Legolas; Gimli (David Buck) the dwarf; and Frodo's three hobbit companions.
Their attempt to cross the Misty Mountains is foiled by heavy snow, and they are forced into Moria. There, they are attacked by orcs, and Gandalf falls into an abyss while battling a balrog. The remaining Fellowship continue through the elf-haven LothlÃ³rien, where they meet the elf queen Galadriel (Annette Crosbie). Boromir tries to take the Ring from Frodo, and Frodo continue his quest alone; but Sam insists on accompanying him. Boromir is killed by orcs while trying to defend Merry and Pippin. They are captured by the orcs, who intend to take them to Isengard through the land of Rohan. The hobbits escape and flee into Fangorn Forest, where they meet Treebeard (John Westbrook). Aragorn, Gimli, and Legolas track Merry and Pippin into the forest, where they are re-united with Gandalf, who was reborn after destroying the balrog.
The four then ride to Rohan's capital, Edoras, where Gandalf persuades King ThÃ©oden (Philip Stone) that his people are in danger. Aragorn, Gimli, and Legolas then travel to the Helm's Deep. Frodo and Sam discover Gollum stalking them in an attempt to reclaim the ring, and capture him; but spare his life in return for guidance to Mount Doom. Gollum eventually begins plotting against them, and wonders if "she" might help. At Helm's Deep, ThÃ©oden's forces resist the orcs sent by Saruman, until Gandalf arrives with the absent Riders of Rohan, destroying the orc army.

Question: Who is stalking Frodo and Sam?
Answer: Gollum