In this fantasy of good against evil an unknown hobbit named Frodo is entrusted with a magical ring of power. He must guard this ring from the powers of evil until he can finally find a way destroy it. In the first book Frodo is given the ring and goes on a quest to see what he must do with it. In the second and third books Frodo continues his quest until the ring is finally destroyed in Mount Doom.
One of the most disturbing trends in Tolkien's "The Lord of the Rings" saga is the gradual corruption of Frodo the Hobbit. The ring that he is chosen to hold gradually breaks down his willpower, twisting him from the hobbit that does not want to possess the powerful, evil ring, to a character at the end of the trilogy that finds it incredibly hard to part with.
"The Fellowship of the Rings" introduces Frodo as the stereotypical hobbit. He spends his time going on walks, going to parties with his friends, and worrying about the small concerns that happen in the Shire. He does not worry about the outside world, and seems to have very little interest in leaving his home. The first time the reader learns that Frodo is going to play an important role is when he is chosen to hold the ring. After learning from Gandalf how easily the ring could corrupt him, the hobbit is hard pressed to take the ring. He urges Gandalf to let him throw it away, melt it, or have the wizard hold the ring. It is only when he learns that none of these alternatives is viable that he accepts it.
It takes a while for the ring to start influenceing Frodo's actions. It is only at the inn in Bree where the reader first sees these signs. During a raucous sing along at the pub, Frodo decides to end his song by jumping in the air and using the magic of the ring to disappear. Frodo did this despite the warnings by Gandalf about using the ring.
The reader once again sees the corruption when Frodo is at the house of Elrond. There Frodo meets with his uncle Bilbo. When Bilbo asks to see the ring Frodo is very reluctant to show it to him, despite the fact that he knows his good friend had no intention of taking it.
Frodo only becomes acutely aware of the influence of the ring at the end of "The Fellowship of the Ring", when he goes through a strong internal struggle. He describes it as "two powers" striking in him, he felt "perfectly balanced between two points." It is only with great self control that Frodo regains control of himself, and decides that he must seek out the destruction of the ring.
As Frodo continues his journeys the corruption becomes more apparent. Midway through "The Two Towers" Frodo and Sam agree to take Gollum with them on their journey. First though, Frodo forces Gollum to swear an oath that he will not commit treachery. Gollum says he will swear on the ring. It is at this point that an important contrast between Sam, an uncorrupted hobbit, and Frodo, a corrupted hobbit, becomes apparent. Sam says that they should not trust the Gollum's promise, he bases this judgement on his assessment of Gollum's character. Frodo knows he can trust Gollum's promise, the power of the ring is too much for Gollum to resist, Gollum would be bound by any promise he made on the ring. Frodo knows this because of the control the ring has over himself.
Once again in the second volume of "The Lord of the Rings" corruption makes itself apparent when the hobbit sees the Morgul King, the leader of the Nine Riders. For a time Frodo cannot control the part of him that wants to reach for the ring.
Perhaps the most obvious point of Frodo's corruption is in "The Return of the King." In this novel Frodo has the opportunity to finally dispose of the ring. But, when Frodo stands at the summit of Mount Doom, the only place that could destroy the ring, he cannot force himself to relinquish it "But I do not choose to do what I came to do. I will not do this deed. The ring is mine." It is only through Gollum biting the ring off of Frodo's hand and then falling into the volcanes that the ring is destroyed.
Even though he is finally rid of the ring, it becomes clear in "The Return of the King" that Frodo will always be scarred by the power of the ring. though in many ways he returns to his old self, the hobbit suffers several disorders. On the anniversary of the loss of the ring, he suffers nausea. Also, because of the evil he can never have children. Perhaps due to the influence of the ring Frodo withdrawals from the other hobbits when he returns to the Shire, he no longer feels much need to socialize. He soon realizes that the only place for him is the havens.
Though in the end he was completely corrupted by the power of the ring, Frodo is the strongest character in Tolkien's series. When asked to take on a mission that might result in his death, he did so. When he realized the power of the ring, and knew what it was doing to him, he did not give in to the temptation to rid himself of it, or give it to the many unsavory, power hungry characters, that would have gladly taken it from him. "The Lord of the Rings" in many ways resembles a traditional heroic tragedy. The hero leavess the garden, manages to accomplish his goal, but only at great cost to himself, and returns to the garden a sad defeated winner. Tolkien emphasizes the tragic part of his trilogy by the ironic twist of having the hero leave the garden. Frodo went through so much to save his homeland, but found that he was too different a person to enjoy it when he came back. Why exactly Tolkien opted for the tragic hero ending, over the glorious returning hero ending is not clear. Perhaps in Frodo he was trying to say that evil can never be completely stamped out, it forever lurks inside us, and that when it is brought to the forefront, it simply cannot be driven back, no matter how much of a simple happy hobbit we might have been.