Mr Johnson is running around like a madman in the middle of the night, and that's a bad idea, what with all the monsters and zombies out there. He's also terrified of the pink ghost, but that ghost is there to help him. Eat the zombies that want to kill Mr Johnson, clear the way for him and make him jump over monsters and torches and holes in the ground.
Use the mouse to control the ghost. Click to scare Mr Johnson, use A to interact with the monsters and other obstacles.