Vicky Van

Chester Calhoun lives with his sister and his aunt in a house on the upper east side, and across the street lives beautiful and mysterious society hostess Victoria Van Allen, known to her friends as Vicky Van. Vicky is a an enigma. She lives in a stunningly appointed house with a servant but no one really knows anything about her. She’s vivacious and a little bit Bohemian, but entirely respectable. 
Vicky often hosts bridge parties for well-heeled New York socialites.  One night, a wealthy millionaire is stabbed to death at one of these salons, and Vicky Van disappears before the police can be summoned.

Chester is convinced that Vicky didn’t do it, despite the circumstances. The police discover that the millionaire was not merely a random millionaire, but a well-known businessman with ties to Vicky’s past.  

Fleming Stone is summoned and for once he has an assistant. Fibsy is one of the rare sidekicks who is actually allowed to figure out the solution to the mystery. The surprise twist ending is one of Carolyn Wells’ best.