For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
Christopher Newman runs into a pretty young woman named Noémie at the Louvre and offers to buy a painting off of her. He also runs into Tom Tristram, an old war pal who invites him back to meet his wife.
The Tristrams introduce Newman to the beautiful and unattainable Claire de Cintre, a widow whose family is intent on her marrying well. Newman manages to persuade Claire and her family to give him a shot after a courtship period of six months. He's overjoyed when Claire accepts his proposal.
Act II
Newman is extra-suspicious when a rich cousin named Lord Deepmere shows up at the engagement party. Although Claire seems to care for Newman, she dumps him soon after.
Around the same time, Claire's brother and Newman's good buddy, Valentin, gets in a duel over the crafty Noémie. Newman sits at Valentin's deathbed and hears about how a family secret could help him win Claire back.
Act III
Newman finds out the deep, dark family secret from Mrs. Bread: apparently, Claire's mom and brother poisoned her dad. Yeeps.
Newman threatens to go public, but what he really wants is to have Claire back. When Claire's mom and brother basically tell him to do his worst, he decides to take a vacation in London. By the time Newman returns, he's cooled down. He burns the letter and vows to move on with his life.