Marie Clifton [Serah D'Laine] is set to inherit two diamonds, called the “mother and daughter”, left to her by her late mother. Her stepfather, Jay Clifton [Brad Johnson], challenges the will, arguing that Marie isn’t ready to handle such a responsibility, but his real motive is to seize the diamonds for himself. At a sexual education seminar at Marie's school, Dr. Chad Johnson [Ron Melendez] and Kristen Richards [Dina Meyer] discuss sex crimes, and Richards confides that she was a victim of an anonymous rapist many years ago, adding a personal sting to the case they’re about to pursue.
At Marie's swim meet, Jay encounters Elena Sandoval [Sandra McCoy], and invites her to Marie's eighteenth birthday party. Elena attends, but Marie coldly tells her she is not welcome. Jay comforts Elena and brings her to the construction site of one of his buildings for privacy, where Elena later alleges that Jay raped her. Detective Michael Morrison [Linden Ashby] is assigned to the case, alongside Richards, while Dr. Chad Johnson is tasked with documenting Elena's injuries and testifies in court that Elena was raped.
Marie grows suspicious of Elena’s motives, concluding she’s after money, and urges Jay to pay her off. When Jay reveals he’s broke, Marie proposes selling the diamonds. Jay agrees and even revokes his claim to the will, handing Marie custody of the diamonds so she can sell them. What follows is alleged to be a carefully orchestrated ploy between Elena, Marie, and Chad to seize the diamonds, and the three of them are described as sharing a sexual relationship.
Jay believes Elena will recant once paid, but in the next court session she testifies that he also threatened to kill her. Jay is sent to prison, yet Richards grows wary of Elena’s behavior. She and Morrison search Elena's trailer and uncover that Elena has collected information about Kristen's rape to bolster her testimony. The detectives confront Jay and surface the possibility that Marie, Elena, and Chad are colluding.
When they question Chad, he fears exposure and turns on Marie, drugging her and stealing the diamonds. Marie and Elena pursue Chad into the woods, where Marie kills him with a tire iron. She then meets the diamond buyer Chad arranged, only to learn the diamonds are fake. Elena, left to deal with Chad’s body, is caught by Richards and Morrison. They assign Elena a task: wear a wire to get Marie to confess to killing Chad, which would lessen Elena’s own charges.
Elena goes to Marie and pretends to go along with a plan to extract the real diamonds from Jay’s safe at the construction site. Throughout the scheme, Elena repeatedly tries to coax a confession from Marie, but to no avail. When the safe is finally opened, Elena pulls a gun on Marie and flees with the diamonds, sparking a chase. Richards and Morrison, watching from nearby, intervene as the two end up in a tense standoff on the site. In the ensuing confrontation, Richards shoots Marie dead.
In the aftermath, Elena claims there were no diamonds, and Richards escorts her away. The twist is revealed: Richards and Elena are mother and daughter; Jay was the man who raped Kristen years earlier, and he fathered Elena. The two of them dispose of him by dosing his drink and leaving him to die. The credits roll with scenes detailing how they pulled off their plan, leaving viewers with a chilling look at how a scheme of vengeance and manipulation came together.
