The Continuing Case of Manny Tippitoes

A young girl awakes in her room to see a strange man singing a catchy song. Meanwhile, her uncle, the youngest detective on the force, is handed an old leather attache case. He is told it contains the results of over 100 years of secret police investigations.
Working together, and separately, Marcella and "Uncle Detective" follow a trail that leads past Victorian detectives, singing waiters, vaudeville showmen, 1930s Hollywood, World War Two and comic book heroes to the present day.
Who is breaking into the homes of the city's richest citizens? Why can't the police catch this intruder? And what's the deal with all the socks?