She's used to finding laughs in catastrophe. But Rose Byrne is only now going to the edge

After stealing focus in everything from “Bridesmaids” to “Insidious,” Rose Byrne unravels beautifully in “If I Had Legs I’d Kick You,” a bold, career-best turn. 0:00 0:00 1x

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NEW YORK — Rose Byrne likes the idea of walking on a tightrope. It’s a metaphor she brings up more than once when we discuss her bracing performance as an overextended mother caring for a severely ill child in the upcoming film “If I Had Legs I’d Kick You.”

“Anything dealing with motherhood and shame around motherhood, whether it’s disappointment, failure — she’s got this line in the movie, ‘I wasn’t meant to do this’ — these are pretty radical things to say,” Byrne explains. “People aren’t comfortable with that. So perfo