Mandy Hope loves animals more than anything else. She knows quite a lot about them too; both her parents are vets and Mandy helps out in their surgery, Animal Ark. It's half-term and Mandy and James are staying in a Welsh fishing village. Mandy is excited to spot some whales out at sea. But next morning, on of them is trapped in the harbour. The gentle giant can't find her way out, but if she doesn't, she will die - and so will her baby, who is waiting for her. Can Mandy and James come up with a rescue plan?