Everything except her child; from the moment James Wilkie was born, she found she orbited around him. "Having a child changes you," says Parker. "Before him, I would have sacrificed myself completely for my work." After him, she didn't even want to sacrifice giving a bedtime bath. "You cross the threshold of your home, and if your baby is awake, you drop everything and run. You could be exhausted, upset, discouraged, disappointed. And you see him and it just changes."

Born in Ohio to a working-class family that moved to New Jersey when she was 9, Parker is one of eight children. As a mom, she "knew in her heart that things run smoother when there is a real structure in place," says Nixon. But both she and Broderick, who is currently on Broadway in The Producers, have long and unpredictable hours. With the help of a nanny during the week, Parker did her best to keep James Wilkie's life consistent – morning playtime at a park near their Greenwich Village brownstone followed by a snack and a nap at noon – and connected to her own.

With a crib, a rocker and toys in her dressing room, she often brought him to the City set. There, her bond with her son – named Wilkie after a favorite 19th-century British writer, Wilkie Collins – was clear. "Sarah's a natural," says executive producer King. "She doesn't overly fuss, it's very nonprecious." Whether called to a fitting or to shoot a scene, Parker happily passed James Wilkie to the nearest crew member – or just left him in her lap. Says King, with a laugh: "We had a couple of takes where all of a sudden you'd hear this little tiny peep. And Sarah would go 'Sorry!' "

Still, even the closeness was at times frustrating. Take the day in the first week of January when James Wilkie, on the set, took his first steps. "He came back to my dressing room and his nanny said to me, 'Look at him.' And then she said, 'Walk to Mama.' And he walked right over to me," recalls Parker. "It was just incredible." But the next thing she knew, she was called back to work – and once again found herself torn. Says she: "It was so difficult for me to walk away."

This is an online excerpt of PEOPLE magazine's cover package.

• By KAREN S. SCHNEIDER. COURTNEY RUBIN in Paris and NATASHA STOYNOFF in New York City