Mac goes on vacation in Las Vegas to meet his girlfriend, a tennis professional (the first of six "girlfriends-of-the-week" who highlighted the "McMillan" series"). While she's preparing for a banquet at a Vegas tennis tournament, she's met by a man who presents her with her stepson's prize ring ("if I had been less civilized, I would have given you his finger to go with it"). The stepson, it appears, is being held hostage for the priceless diamond necklace the tennis pro is wearing, the last of her inheritance from her late husband. Mac quickly finds that it's a scam (the stepson was holed up with his girlfriend and was tricked into giving over the ring). Before the con man responsible for the theft can be found, he's murdered with a gun belonging to the tennis pro. Now Mac must clear his girlfriend of the murder and recover the necklace.