An adventure series for young viewers. A group of children, accompanied by their guardian, Filip, arrive at a sanatorium for allergy sufferers. Inside an old piano, they discover stairs to a hidden room containing a mysterious device. It's a Change Machine. Whatever, or whoever, is placed inside it transforms into something entirely different. The children's guardian takes on the role of guinea pig in an intriguing experiment. He enters the Machine. Moments later, a real rabbit emerges from the device.