Bard took the bow into his hands. He addressed the last arrow in his quiver.
"Black arrow, he said, 'you have never failed me.'
From the sky the great Wyrm settled beside him.
'But you have failed it' hissed Smaug, 'which arrow did you choose last? Yeah thought so."
Upon hearing the truth, the men of Dale immediately switched sides. Bard fell backwards into a swimming pool, and everyone laughed (Smaug later devoured Bard as is customary with his fascinating and endangered species).