For the firm of Carpenter and Quincannon, Professional Detective Services, stopping extortionists is not only grand, but excitingly lucrative.When a pleasant afternoon's bicycling through Golden Gate Park with a friend ends with the revelation of threatening letters, followed by a gunshot in a mansion garden, Sabina Carpenter knows this is a case that demands her immediate and undivided attention.The questions her partner John Quincannon has to unravel...