JoJo and Gran Gran are enjoying a canal walk when they meet Ned and Monty, who need some help. Ned’s looking for the lock key, so they can take their canal boat through the lock and along the canal. JoJo decides she and Gran Gran can help with the search – where could the key be? And how can they get moving quickly enough to solve the canal traffic jam that’s building up? It’s time for a Gran Gran plan.