Paula Santos, the owner of Captain's Cove Amusement Park in New Jersey, has asked Nancy for help because there have been mysterious things happening at the park. First, the lead horse disappeared off the carousel. After that the carousel began mysteriously starting up in the middle of the night. Then the roller coaster suddenly lost power, resulting in a serious accident. The park is shut down until the city knows what caused it. There is a rumor going around that the park is cursed. Are the painted ponies searching for their missing lead horse, or is there another explanation for the midnight rides?