Complex sentence: Max's marriage to Kate (Melanie Griffith) is jeopardized by someone desperate to retrieve the film, a blackmailer who sends Kate a copy of a film showing her husband and Allison having sex in the same motel room.
Split into simpler sentences: Max's marriage to Kate (Melanie Griffith) is jeopardized by someone desperate to retrieve the film. Then a blackmailer drops off a film to Kate showing her husband and Allison having sex in the same motel room.