The set of the 1954 romantic comedy Sabrina was tense. Script changes occurred daily, a leading man clashed with the director and two of the costars hated each other on sight. Only Audrey Hepburn and William Holden seemed to have having a good time — they were in love!

Sabrina, the story of a chauffeur ’s daughter who has to choose between two wealthy brothers, would become a classic and garner Audrey her second Oscar nomination. Even though her romance with Bill, her married costar, would turn out to be a disappointment, it would set Audrey on the path to making her dreams of a family come true.

Although Roman Holiday had already made Audrey a star, she still felt like a novice on a film set when Sabrina began production. She called Bill, who played David, the playboy son, her “guardian angel” for taking her under his wing. Before long, the pair were laughing together over post-filming cocktails with their director, Billy Wilder.

The film’s second lead, Humphrey Bogart, was offended. “We didn’t think of inviting Bogart,” Wilder later claimed. In truth, Bogie, who had replaced Cary Grant in the role of older brother Linus, felt miscast and clashed frequently with Wilder and Bill, whom he called “Smilin’ Jim.”

Audrey and Bill remained above the fray. Before long, they were enjoying rendezvous for just two. They conducted their romance in secret, conscious that gossip would get Audrey branded a homewrecker and potentially destroy her career.

Audrey was, of course, aware that Bill was married. She had even met Bill’s wife, Ardis, but she still dreamed they’d find a way to marry and start a family. She called him “the most handsome man [she’d] ever met.”

Those schoolgirl hopes were cruelly dashed when Bill, already a father of three, confessed that he had undergone a vasectomy. “He also showed no signs of getting a divorce. For a woman who cared about being married to a decent guy and having children, it was a one-two punch,” says Barry Paris, author of the biography Audrey Hepburn. A few months later, Audrey and Mel Ferrer, whom she’d previously dated, announced their engagement at a party arranged by Paramount Studios at Bill and Ardis’ home. Her love affair with Bill had been bittersweet and brief, but they would remain lifelong friends.