The city streets buzzed with late morning life, vendors calling out their specials, the scent of roasted chestnuts mixing with exhaust fumes. Celine balanced a paper bag of groceries against her hip, her other hand clutching a list she had half-finished scribbling on the subway. It felt almost normal to be outside the café—even if normal had been hard to come by lately.

She slowed near a corner bakery, distracted by the neat rows of pastries gleaming in the window. That was when someone ...