Donkey Kong Junior must save his father from Mario by putting the key or keys in the stage into all of the locks. Mario attempts to stop Donkey Kong Junior by releasing the many animals he controls to knock Donkey Kong Junior off the vines and platforms. Donkey Kong Junior defeats Mario if the player completes the fourth stage by putting all six keys in their locks, making the floor disappear. Donkey Kong Junior catches Donkey Kong while Mario falls onto the ground.