There's trouble for Trevor Evans as the school bus swerves off the road and breaks down in the Pontypandy hills. Unfortunately, mobile phones have no signal up in the Welsh hills and he is stranded - with a beast about. Fireman Sam comes to the rescue, with the assistance of Tom in the helicopter. Then they search for Trevor, who made an attempt of finding help. In the end everyone is safe and they go home. Norman spots a black animal passing over the road just before the bus rounds a corner, but when he tells everyone else about his sighting, nobody believes him.