Ranger Hamza and the Ramblers discover how chalk streams play an important role in their environment. They find out that they are a very special type of stream, with cool, clear water that is perfect for lots of plants to grow. They learn that many different creatures like to make their home in and around the streams too. On the way, they pretend to be kingfishers and herons and take a close look at some animals that live in the chalk stream.