The Grandfather Club

All of the school clubs have been cancelled, effective immediately. All except one… Lucy and Hobo can’t understand why everyone at school has joined the gardening club. They also can’t understand why no one is doing any gardening! Why are the students constructing a gigantic greenhouse? And why does it need such a powerful heating system? But, more to the point, what sort of plants will this greenhouse be the home to? Will Lucy and Hobo be able to solve this mystery or have the seeds of destruction already been sown?