The Fellowship of the Ring Book 2, Chapter 10
They rest for the night and Aragorn sits awake with the watch, worried that the enemy is near. Frodo draws his sword and its faint glow tells him that orcs are somewhere about. This disheartens Aragorn. They eat breakfast and then have a council to decide what to do next. The burden of the decision falls on Frodo, the bearer of the ring. He asks the group for an hour longer to make his decision. Sam thinks that it is an easy answer. Frodo walks away from the rest.
Boromir follows him. He comes up to the hobbit and asks if he can talk to him alone. He thinks that whenever they talk as a group they can never come to any sort of an agreement because there is always an argument. He is sure that together they can find wisdom. He tells Frodo that they should not fear the ring so much. He thinks it can be used for good as well as evil. He tells Frodo that the ring can corrupt elves and dwarves and wizards, but men are stronger, and will be able to resist it. If he had the ring, he could command a great army and drive away the hosts of Mordor. His mannerisms become more eager as he speaks more loudly and says that it is folly to destroy something as powerful as the ring. He tells Frodo that he should go to Gondor and puts his hand on the Hobbit's shoulder. Frodo says he will not give him the ring and Boromir demands it. He tells him that he could take it if he wanted to. Frodo slips on the ring and disappears. Boromir screams. Frodo runs away and the ring makes him see the land around him much more clearly. For a great distance he can see all round. He looks upon Minas Tirith and knows that the dark lord is stronger than Gondor. He feels the eye of Sauron looking for him. A power struggles within to control him and he slips off the ring. There is silence. The way he must go is clear. He decides he must travel alone into Mordor. He puts the ring back on.
Aragorn is addressing the others and debating where they should go when Boromir returns. They hadn't noticed that he had followed the Hobbit. Sam knows that Frodo isn't all right when Boromir returns. Aragorn calls out for the Hobbit and asks Boromir what happened. He says "'I grew angry and he left me. He vanished.'" Book 2, Chapter 10, pg. 475. He omits that he reached for the ring. Aragorn doubts his story but is more concerned about Frodo. They decide to split up and search for him. Sam thinks of where he will find Frodo and looks near the boats. He falls in the water on purpose and Frodo pulls him out. He tells Sam that he is going into Mordor and warns him not to be a hindrance. Sam tells him that he is going with him and Frodo relents. He is happy not to enter alone. They poke holes in the other boats and take theirs downstream. They come to land after a great amount of time and start on a path that will take them into the land of the shadow.