Blotto, Twinks and the dead Dowager Duchess

"The aristocratic but slow-witted Blotto and his extremely brainy sister Twinks are attending a weekend house party when their hostess, the Dowager Duchess of Melmont, is murdered. An amateur detective, conveniently staying for the weekend, deduces that the Lyminster family's chauffeur, Corky Froggett, is the murderer. But Blotto and Twinks are unconvinced, and the only way to prove Corky's innocence is to find the real perpetrator."--Publisher description.