The Coridae Key is the sequel to Lowarth Toll. Arthur Snade has inherited a house in Torleith, from his Aunt Emily. He spent some time visiting her and reading to her, when he was on holiday in Cornwall. Emily's brother and sister found a note from Charles Trewartha reminding Emily not to forget about the family treasure. They did this when Emily was taken to hospital having been found on her hall floor. Emily knew nothing of the treasure, so they systematically pulled her house apart in an effort to find it. When Emily died, they found out that she had left everything to Arthur, so they started on Arthur. They presumed he knew about the treasure. He knew even less than Emily did. Arthur is rescued from a further beating by an heir hunter. Arthur inherits Lowarth Toll and moves to Cornwall. He meets up with his childhood sweetheart, Jenny, when she stops to give him a lift as he walks home with several bags of shopping. The family still hasn't given up on finding the treasure themselves. Having watched Arthur find something in the field behind Lowarth Toll, they investigate it for themselves during the night, with tragic consequences. Arthur and Jenny keep working at the clues and discover 4 pieces of treasure. They are made of a dull coloured, very heavy metal. There is a crown, a collar, a ring and a bangle. They report the find to the authorities and the treasure is taken to the British Museum to be assessed. One morning when they open their vault they find the treasure has gone, but no one has been in the vault. Arthur finds the treasure inside a safe he is having delivered to Lowarth Toll. He is given the instructions to hide the treasure away again until the right time, so he does. The Coridae Key takes up the story from that point. It tells of how the treasure was made and how it was brought to Cornwall many centuries ago. Arthur and Jenny try to find more about the treasure and where it might have come from. Events come together to make this 'the right time' and so they find out a little bit more about the treasure and eventually find The Coridae Key.