An older man, Andrew Marsh, is seen viewing a homemade pornographic tape. It is later revealed the man died from complications stemming from erotic asphyxiation. The main suspect is the woman having sex with Marsh in the film, Rebecca Carlson (Madonna), who after being charged with murder is represented by lawyer Frank Dulaney (Willem Dafoe).
The trial begins in Portland, Oregon and it isn't long before Rebecca and Frank enter a sadomasochistic sexual relationship behind the back of Dulaney's unsuspecting wife (Julianne Moore). Their rough sex goes so far that Rebecca drips hot candle wax onto Frank.
Rebecca proclaims her innocence to Frank in private as well as in court, but the prosecutor and district attorney Robert Garrett (Joe Mantegna) is out to prove that Rebecca Carlson deliberately killed Marsh in bed with sex to receive the $8 million he left her in his will.
The testimony of Marsh's private secretary, Joanne Braslow (Anne Archer), reveals that he also had a sexual relationship with her that could have contributed to his death, casting a reasonable doubt as to Rebecca's guilt.
Frank can't resist Rebecca sexually but he doesn't trust her. His wife sees telltale marks on his flesh and realizes he's been having an affair. Rebecca is shown in court to have had previous sexual relationships with a number of older rich men, including Jeffery Roston (Frank Langella), in which her lovemaking was just as rough, indicating that what she did with Marsh was not unusual.
Taking the witness stand, Rebecca's emotional testimony that she did not mean to cause her older husband's death convinces the jury, which acquits her. Before leaving court, she mockingly thanks Frank for getting a guilty client off. Frank finally becomes fully aware that Rebecca indeed killed March delibrately with sex and worse still, he cannot repeat what she said because of the attorney-client privilage law. Frank also knows that Rebecca cannot be tried again because of the so-called "double jeopardy" law which states that no one can be tried twice for the same crime, even if the accused confesses or new evidence surfaces afterwords.
Frank goes that night to Carlson's home, where he finds her with Marsh's doctor, Alan Payley (Jürgen Prochnow), freely discussing the way they both conspired to kill Marsh for his money. She's free and clear, but taunts Payley by telling him to lie low (as he could be convicted of perjury) and to leave because "I've already forgotten you."
Rebecca bluntly tells Frank that her sexual prowess is how she is able to make men do anything... including him. An enraged Payley lashes out at Rebecca physically and, after Dulaney pulls him off, Payley shoots her twice. She plunges from a window to her death in the water below.
In the final scene, as the police take Payley away, Frank turns to Garrett as the dead Rebecca is taken away and says, "You should have won the case Rob." Garrett coldly replies, "I did."