Once the Philistines had seized the Chest of God, they took it from Ebenezer to Ashdod,
brought it into the shrine of Dagon, and placed it alongside the idol of Dagon.
Next morning when the citizens of Ashdod got up, they were shocked to find Dagon toppled from his place, flat on his face before the Chest of God. They picked him up and put him back where he belonged.
First thing the next morning they found him again, toppled and flat on his face before the Chest of God. Dagon's head and arms were broken off, strewn across the entrance. Only his torso was in one piece.
(That's why even today, the priests of Dagon and visitors to the Dagon shrine in Ashdod avoid stepping on the threshold.)