Billie doesn't feel well until she returns to Jack being her best friend and Rebecca her second-best friend.

Jack's whole class is coming to his birthday party. It's going to be awesome! But what will he do when his best friend is too sick to come?

"Is being best friends enough to save a whole town? Polly and Buster have always believed that witches and monsters can be friends, but it seems no one else agrees. While the witches are furious and the monsters are in uproar, a much greater menace lurks nearby. Can Polly and Buster bring everyone together in time to save their town?"--Provided by the publisher.

"Billie loves Rebecca's older sister. They make her feel so grown-up! But is Billie grown-up enough to handle the scary movies they like?"--Back cover.

"Billie and the Secret Mystery Club are investigating their most serious mystery yet. Someone has taken something from the principal's office at school! Who would have done such a terrible thing? And when one of Billie's friends becomes a suspect, will Billie even know who to trust anymore?"--From the publisher's web site.

"Someone has stolen all of the ripe strawberries from Mika's garden! The Secret Mystery Club is determined to work out who it was. Could it have been the gardener? Or was it Billie's neighbor Andrea, who just made a huge batch of strawberry jam? Whoever it was, they won't get far--not with the SMC on the case"--Back cover.

"Billie and the Secret Mystery Club have a new case to solve. Who put leaves in Rebecca's sandwich? It's a real mystery. Soon everyone suspects Benny, but could they have the wrong kid? It's up to the SMC to find the real culprit!"--Back cover.