The Women Behind ‘You’ on Creating This Fall’s Darkest, and Most Timely, Romance

Sera Gamble and Caroline Kepnes had just wrapped a long day on the set of their new Lifetime romantic thriller, “You,” and all they wanted to do was celebrate.

It was August 2017, sometime between midnight and last call. Ms. Gamble, a writer and producer who developed “You” with Greg Berlanti, and Ms. Kepnes, who wrote the novel it’s based on, were in New York City, where the show is both set and shot. Production had just begun on the series, which will premiere Sept. 9, and the women had decamped to a bar for a hard-earned drink and soon became engrossed in a conversation about their characters. Then, as Ms. Gamble recalled, “This quite drunk guy sits down next to us and just starts talking.”