Merkle was the baserunner on first during the 1908 instance. He failed to touch second base. The ball (and this story has many POVs) was believed to be tossed to fans by an exiting Giants player/ pitcher (the clubhouses at the Polo Grounds were behind CF) to a fan or in the stands. the Cubs 2B Evers went to chase after the ball, as Merkle exited the field w/o touching second (fans were storming the field, which was not uncommon in this era, after the base hit to CF, which would've scored the run from third making the final 2-1 Giants. Long story short, Evers brings 'a' ball to second base and touches second for the force out, and the umpires (there were only two umps working the game) were consulted during a wild scene. Merkle ruled out, protests, mayhem, hearings, game ordered replayed weeks later, Giants lose, lose pennant by a game.
edited massively for brevity.
