Meet Bradley, Brian, Lucy, and Nate - the younger siblings of the A to Z Mysteries gang. This new generation is solving their own mysteries in the new Calendar Mysteries series. In January Joker, the kids believe that aliens have invaded and are abducting people from the town of Green Lawn. Bradley has seen spooky lights that wake him from a sound sleep. There are strange prints in the snow and their pony suddenly disappears. Who could be causing all this trouble? Have aliens really invaded Green Lawn? Will the kids be able to solve the mystery in time?