One player is chosen to be the "mouse trap" operator. They are blindfolded and stand on the side of the play area. Four players are then chosen and stand holding hands and facing each other. They hold their hands up in the air. The other players are mice and then must walk through the trap. The operator calls out "spring the trap" every so often, trying to catch one of the mice. If the get caught they then become part of the trap making it larger and harder to get through. When there is one mouse left they then take a turn at being the operator. The last operator is then part of the trap for the next round. Everyone should be an operator at least once.
Source: From the original site.