On April 19, 1986, the Cardinals took down the Expos 9-6 in a 17-inning marathon in Montreal. The Expos looked like they were going to sail to victory until the Birds tied it up 4-4 in the ninth. Each team scored in the thirteenth and fourteenth innings to keep the contest going, before an unlikely hero put the Cardinals up for good in the seventeenth. The hero was reliever Tim Conroy, who came to the plate with the bases loaded, worked a walk, and forced in Terry Pendleton to give the Cardinals a 7-6 lead. It was Conroy's first major league at-bat, who had been in the big leagues for 8 seasons up to that point. Willie McGee followed Conroy with a two-run double for a little insurance, before Conroy set down the side in order to secure the win. 5 hours and 22 minutes after the game began the Cardinals were victorious.
Check out the box score here: http://www.baseball-reference.com/boxes/MON/MON198604190.shtml