Mount Doom is the 3rd chapter in the second book of The Return of the King (novel). In this chapter, Frodo and Sam reach Mount Doom and the Crack of Doom. Yet just as Frodo is about to throw the Ring into Mount Doom, he succumbs to the Ring's power and refuses to let it go. Just then, Gollum, who had been following the pair still, attacks Frodo and bites off his finger with the Ring. Gollum gloats over getting his prize back, but loses his balance and falls into the lava below, taking the One Ring with him. The Ring is thus destroyed, freeing Middle-earth from Sauron's power.