Little Truff senses something is wrong. At sea, in a boat with her family, she tugs her master to the stern. 'A whale's out there. It hasnt moved,' Dad tells his family. 'I think it's tangled in a net and trying to get free.' What can we do to save the whale? Truff thinks. One slap from her tail could kill us - but we can't just sit here and watch the humpback die ... '