William Wyler's 1939 film Wuthering Heights, based on Emily Brontë's 1847 novel, is a love story involving a young lady and two men. Catherine, the focus of both men's love, leads a double life around them.
Heathcliff, Catherine's first and true love is portrayed as her brother's gypsy servant. In the book, he is the young boy her father brought home to raise as his own. After her father dies, her brother turns him into his servant and treats him as one. Catherine and Heathcliff bond instantly and eventually fall in love. In the movie, Heathcliff (Laurence Olivier), and Catherine (Merle Oberon) sneak over to the house of their rich neighbors, the Lintons, to see what they are doing. There is a ball going on, so they hop over the fence to get a better look. A dog bites Catherine's leg, and she must stay at the neighbors until she is healed. That is the place that she meets Edgar Linton, played by David Niven.
Edgar is the son of the rich neighbors. Instead of being a servant, he has servants. He falls in love with Catherine, but Catherine loves Heathcliff. She is worried about her future if she marries Heathcliff, so she starts to date Edgar. This is the beginning of Catherine's double life.
Catherine really gets into her two lives, even using costumes. For Heathcliff, her poor, true love, she dresses down. She wears loose fitting, old clothes that are dirty. Her hair is down and messy. When Edgar comes for a visit, she wears new, clean dresses that fit her nicely, with a corset and hoop under her skirt. She even puts her hair up with perfect curls falling down.
She tried to convince the men that she is who they want her to be. She plays up to the fact that Heathcliff and Edgar live such different lives. By throwing on some old clothes and not worrying about being clean cut or her hair, she could convince Heathcliff that she is the same girl he fell in love with. When she dresses up in expensive dresses with her hair neatly done and smelling good, she can convince Edgar she is a new girl with fine taste and style.
She does well with her secret life even though she lives with Heathcliff. He realizes the truth only when Catherine tells Ellen Dean (Flora Robson) about the two paths she could take. Ultimately she has to choose one way or the other, and it seems prosperity and Edgar's love win over sacrifice and true love.