Zyzzyx Rd (2006)

The family man accountant Grant travels to Las Vegas and meets the lascivious "Lolita" Marissa in a casino. While in the motel with Marissa, her violent ex-boyfriend Joey surprises them on the bed, hits Grant on the head, but he kills Joey. Grant brings Joey's body to bury in the desert Zyzzyx Road, but after digging a grave, he finds that the body is missing in the trunk of his car. Grant chases Joey with a shovel in the desert, and when he finds the man hidden in a abandoned mine, Joey discloses a secret about Marissa.