Hessen Conspiracy
(2009)

Though it seems for awhile that Kathy Nash (Lyne Renee) has sold out Jack Durant (Billy Zane), it turns out they are playing a con to sell Ben Cassidy (Michael Bowen) the diamonds he already bought off of Roy Tarlton (Rudolf Segers), who had stolen them from Kathy and Jack, thinking they were going to screw him out his cut.

Kathy switches out the real diamonds with fakes Jack bought earlier then places them in a restroom at the buy meeting. Jack recovers them and resells them to Cassidy for two million. Tarlton tries to kill Jack on the way out but he kills him. Jack walks away as Cassidy is arrested by Capt. Michael Savern (Gene Pyrz) for possessing the diamonds. Jack had promised Savern he would catch Cassidy in the act; and in return for turning state's evidence, Jack would get a proper discharge and immunity.

Jack meets up with Kathy  so they can disappear. Jack says Savern thinks Tarlton is the buyer, but he will chasing "a dead man." Jack says he wants to marry Kathy and he knows she is the one because she didn't abandon him. The lovers drive off into the night, much richer.

Thanks Spectre!