It all started with one mysterious briefcase....

When Allie's father dies, her half sister, Kat, is left in charge of his detective agency -- and of Allie. Despite the many changes in her life, Allie can't help being excited by the possibility of being close to some real private-eye adventures, the kind she is always daydreaming about.

So when a man comes to the agency asking Kat to guard his briefcase, it looks like Allie will get her chance to investigate. But when Allie breaks into the briefcase, she makes a shocking discovery. And when she begins asking around, she realizes she may have taken on more than she bargained for. Whoever wants the briefcase kept safe desperately needs the agency's help, and whoever wants them uncovered will do anything to find them....