Under instructions from big boss Tony, local mobster boss Vince Shackman leans heavily on race horse trainer Mike Gann to settle his gambling debts by fixing a race, which takes quite a lot, including making a Panamese illegal jockey be replaced 'sick' by greenhorn Tracy Macgill, a niece of Jessica, who made a stop-over on the way to San Francisco to see her debut. When Tracey is arrested for the tranquilizer gun murder of Jack Bowen, Jessica fears the police won't solve the case and takes crash courses in betting and running a stable while investigating everybody involved, including unethical betting by the track security chief...
—KGF Vissers