Helen has been affected the dark bacteria that forces her to stay in the dark. Thomas can stay alive by walking in places that are illuminated by various, dynamic light sources like a flashlight or a lantern. In each level the player must guide both players to the exit with as few steps as possible. They also have to find a cure for Helen's affliction. Completing the levels with good scores unlocks cheat codes.

Helen has been affected the dark bacteria that forces her to stay in the dark. Thomas can stay alive by walking in places that are illuminated by various, dynamic light sources like a flashlight or a lantern. In each level the player must guide both players to the exit with as few steps as possible. They also have to find a cure for Helen's affliction. Completing the levels with good scores unlocks cheat codes.