Trying to find his way out. Bilbo went on down to the roots of the mountains, until he could go no further. At the bottom of the tunnel lay a cold lake far from the light, and on an island of rock in the water lived Gollum. He was a loathsome little creature: he paddled a small boat with his large flat feet, peering with pale luminous eyes and catching blind fish with his long fingers, and eating them raw. He ate any living thing, even orc, if he could catch it and strangle it without a struggle. He possessed a secret treasure that had come to him long ages ago, when he still lived in the light: a ring of gold that made its wearer invisible. It was the one thing he loved, his 'precious', and he talked to it, even when it was not with him. For he kept it hidden safe in a hole on his island, except when he was hunting or spying on the orcs of the mines.
Maybe he would have attacked Bilbo at once, if the ring had been on him when they met; but it was not, and the hobbit held in his hand an Elvish knife, which served him as a sword. So to gain time Gollum challenged Bilbo to the Riddle-game, saying that if he asked a riddle which Bilbo could not guess, then he would kill him and eat him; but if Bilbo defeated him, then he would do as Bilbo wished: he would lead him to a way out of the tunnels.
Since he was lost in the dark without hope, and could neither go on nor back. Bilbo accepted the challenge; and they asked one another many riddles. In the end Bilbo won the game, more by luck (as it seemed) than by wits; for he was stumped at last for a riddle to ask, and cried out, as his hand came upon the ring he lad picked up and forgotten:
The Authorities, it is true, differ whether this last question was a mere 'question' and not a 'riddle' according to the strict rules of the Game; but all agree that, after accepting it and trying to guess the answer, Gollum was bound by his promise. And Bilbo pressed him to keep his word; for the thought came to him that this slimy creature might prove false, even though such promises were held sacred, and of old all but the wickedest things feared to break them. But after ages alone in the dark Gollum’s heart was black, and treachery was in it. He slipped away, and returned to the island, of which Bilbo knew nothing, not far off in the dark water. There, he thought, lay his ring. He was hungry now, and angry, and once his 'precious' was with him he would not fear any weapon at all.
But the ring was not on the island; he had lost it, it was gone. His screech sent a shiver down Bilbo's back, though he did not yet understand what had happened. But Gollum had at last leaped to a guess, too late.
At length they came to a halt before an unseen opening that led to the lower gates of the mines, on the eastward side of the mountains. There Gollum crouched at bay, smelling and listening; and Bilbo was tempted to slay him with his sword. But pity stayed him, and though he kept the ring, in which his only hope lay, he would not use it to help him kill the wretched creature at a disadvantage. In the end, gathering his courage, he leaped over Gollum in the dark, and fled away down the passage, pursued by his enemy's cries of hate and despair: