Mr. Lucky Number

When Thorin Oakenshield set out from his halls in the Blue Mountains at the beginning of the Quest of Erebor, he took with him twelve companions, so his Company numbered thirteen in all. This was considered to be an unlucky number, and so the Dwarves were keen to add a fourteenth member to bring good fortune to the enterprise. Before they had set out, the Wizard Gandalf had already nominated that fourteenth member: the Hobbit Bilbo Baggins, who would act as a stealthy treasure-hunter (or 'burglar' as the Dwarves preferred it) for the expedition.

Thorin and his companions were initially sceptical about including the Hobbit, and their doubts only increased after they met Bilbo, who seemed quite unadventurous. They were nonetheless convinced to take the Hobbit with them, partly at the insistence of Gandalf, and partly because their Company would otherwise remain at the unlucky number of thirteen.

The Quest progressed across Middle-earth through many dangers and difficulties, until at last Bilbo found himself confronted by the Dragon Smaug. Made invisible by his Magic Ring, Bilbo had no wish to reveal his identity to the Dragon, and so instead used a series of riddling names for himself, recounting (among many other such titles) that he was chosen to be the lucky number.

The wily Dragon immediately recognised the implication of this phrase. He called Bilbo 'Mr. Lucky Number', surmising that he was one of a party, and that that party must have numbered thirteen before the Hobbit joined it. Fortunately for Bilbo, the Dragon gained little profit from this deduction. At the same meeting, the Hobbit noted a bare patch in the armour on Smaug's left breast, an opening that Bard the Bowman would use to defeat the Dragon shortly afterward.