OK, usually I'm pretty good at puzzling out these detective movies, but I feel a little in the dark on this one. I understand most of it, but what was the deal with Robert Wagner? I get why he wanted the money, but how in the hell did Harper figure it out?
Harper knew that Taggart (Sampson's pilot), in Vegas, called Eddie (one of the kidnappers, and later the bag man), in Van Nuys, and told him to have the black limo waiting for Sampson when they arrived. Later, when Taggart saved Harper from getting beat up at the Piano lounge, Harper figured Taggart was there to tail him, not just to find him. After that, at Fay's house, when the truck full of illegals arrived, Taggart fired at it, claiming to be shooting at the tires. Harper realized that he wasn't firing at the truck to stop it, but actually warning the driver (Eddie), to make a run for it.
This all came together when Harper learned that Eddie was Betty's brother, after he found out that she and Taggart were romantically involved (when Taggart said he had himself a "real woman").
Of course why any young male with a pulse would choose some over-the-hill junkie, old enough to be his mother, over Pamela Tiffin is beyond me. As far as I'm concerned, that's a major plot hole.
Unc John "We makin' trouble?" Stacy "Yeah" Unc John "What kind?" Stacy "...The forever kind"