You defeated the trolls and saved the waitress! You collect a few sacks of gold coins and a sturdy club that does considerable more damage than your beer bottle.
The old man returns to the saloon with an astonished look on his face, while carrying a handful of color potions. "I am impressed, traveler! You have special abilities. Follow me back to my tower!"

Meanwhile, the waitress is now madly in love with you.
(like this comment) follow the old man to his tower.
(hate this comment) follow the waitress back to her house.