It's been years since Bernie and Libby's parents became estranged from Ada Sinclair's side of the family-though the reasons for the rift are lost to history. The sisters, however, are intrigued when Ada makes contact and tells them about the long-ago deaths of her father and his business partner-both of which were ruled accidental. Ada thinks otherwise-and has a plan. On New Year's Eve, she'll gather a group of guests and read from a diary she's found in her mother's attic that she thinks will expose the culprit. The Simmons sisters agree to provide refreshments for the bash, but when the night arrives, a guest drops dead. In the tumult, the diary disappears. When Ada is arrested for murder, she'll have to hope that Bernie and Libby can provide a resolution before the clock runs out.