Set sail for a terrifying adventure on the high seas. Siblings Billy and Sheena are thrilled to join their uncle, Dr. Deep, aboard his incredible high-tech boat. They are ready for a fun treasure hunt, hoping to uncover hidden riches beneath the waves. But their excitement quickly turns to pure panic when they awaken a two-hundred-year-old sea captain. This ancient pirate refuses to stay peacefully at the bottom of the ocean, and he has brought his creepy crew with him. Billy and Sheena find themselves completely surrounded by danger in the middle of the dark water. As they desperately try to escape the eerie captain, they accidentally steer right into an even bigger mystery. Their journey will eventually lead them to the gates of Horrorland, a theme park where your worst nightmares step right out of the shadows.