At 40, Shahira Fahmy took her first acting class. At 43, she walked the Cannes red carpet for the premiere of her first feature film—the French/Korean drama Claire’s Camera in which she played opposite Isabelle Huppert. Her story of risk and reward is remarkable, even more so because Fahmy already had a successful career, and one that she enjoyed. As an architect, she had her own practice in Cairo, several projects to her name, a teaching post at Columbia University and frequent speaking engagements. Then a set design project sparked her curiosity about acting, and she slowly explored it—to the surprise and, sometimes, disdain of other architects. Now 45, Fahmy is in the middle of another upheaval, as she moves from her near-lifelong home of Cairo to London. Sitting among the pack...