Twins Millie and Charlie Andersen have absolutely no clue about how exciting their summer is about to become. In fact, it looks like it's going to be a very boring summer at Grandma's what with all the dull chores she assigns. An odd neighbor, a very small visitor and a mysterious dark stranger will change all that. Danger is lurking just outside their front door ready to hurl them into a series of challenging events that will make their hearts race and their heads spin. But will they be able to handle it? And what the heck is a honey possum?