This Perry Mason movie has a closed ring of suspects in who killed Robert Culp. All of them John Posey, Jere Burns, Kevin Tighe, Robert Vaughn, and Ken Kercheval have lots of reasons to kill Culp, he was blackmailing the lot of them.
Culp has a really clever scheme going, his victims meet in Las Vegas every year give him and $8000.00 check and declare it as gambling losses as he declares a gambling victory. It's made him a rich man, as rich as the rest of these guys, all of whom he has something on.
But when Posey breaks in waving a gun threatening to kill Culp, he's tailor made as a fall guy. One of them steals his gun and shoots Culp.
The perpetrator has an accomplice steer Posey away from the scene and then disappear so he has no alibi. It's William R. Moses's job to find that accomplice Michelle Scarabelli. In fact Scarabelli has quite a secret of her own.
In casting Burns, Tighe, Vaughn, and Kercheval they got four people who've done some pretty nasty things big screen and small in several movies and programs. You'll not figure out who the perpetrator is.
And that's the necessary ingredient for any Perry Mason story because Raymond Burr does not defend guilty clients.