Rachel, a New York food writer, has broken up with her first husband who had a fixation with hamsters. She falls in love with Mark, a divorced Washington columnist who has a reputation as a lady's man. Neither one believes in the institution of marriage, so of course they get hitched.
They move to Washington and begin renovating their Georgetown brownstone. Soon Rachel is pregnant. Annie is born. At a picnic with friends, Rachel rhapsodies about the joys of motherhood; Mark complains about lost socks. At another get-together, a TV journalist spreads the latest dirt on who is committing adultery. Then Rachel pregnant again discovers that Mark is having an affair with a well-known Washington hostess.
Nora Ephron's screenplay for Heartburn only loosely resembles her 1983 novel. In the book, she wrote: "The infidelity itself is small potatoes compared to the low-level brain damage that results when a hole chunk of your life turns out to be completely different from what you thought it was." During the second half of the film, Rachel leaves Mark, but later returns to him. She tries to pretend everything is the same as it was in the past, but it isn't. Their second daughter is born. Rachel's anger builds and finally spills out in a feat of sweet revenge.
Merly Streep's performance as Rachel is a mixed bag. She accurately conveys her dis-equilibrium as a jilted wife and a loving mother but is unable to pull of the character's final witty step into independence. Jack Nicholson is convincing as Mark, the narcissist Peter Pan male who doesn't know the meaning of guilt or responsibility. In one of the film's best scenes, he serenades their yet unborn child with snatches from songs with "baby" in the lyrics. Yet at the same time, he shares almost nothing in his life with Rachel.
Mike Nichols draws out good performances from Jeff Daniels as Rachel's magazine editor who would like to play a larger role in her life; Stockard Channing and Richard Masur as Mark's friends who grow to cherish Rachel; Catherine O'Hara as a bubble-headed TV reporter; and Steven Hill as Rachel's father who can do little to comfort his daughter because he's too wrapped up in the mess of his own life.
"Marriage is the most dangerous form of love," journalist Michael Ventura has observed. "Count the casualties and you know. It turns many people to stone." The relationship between Mark and Rachel is characterized by a total lack of communication, an absence of intimacy, and pits of loneliness. They expect very little out of this adventure, and in the end, it comes to nothing. That's why despite its comic moments Heartburn is an extremely depressing film.