We're Off to Kill the Wizard

Plot:

When Jessica visits her Kansas relatives, police detective Lieutenant Bert Donovan's family, she is invited by theme park magnate Horatio Baldwin and firmly turns down his project for another one based on horror elements from her mystery books. Shortly after Horatio is found dead in his self-locked office, apparently suicide, but actually got a fatal blow on the head before the shot. After Erica Baldwin becomes a rich widow for the fourth time, she hires Jessica to prove it was murder so the life-insurance can be cleared. Horatio's secretary makes a false confession. ...