PARIS—When a young Frenchwoman showed up early this month at an Islamic State border checkpoint in northern Syria, the extremists controlling that arid expanse were expecting her.
They waved her right through and let her bodyguards accompany her, according to Western counterterrorism officials.
The militants had been told to give Hayat Boumeddiene special treatment by the network of chaperones who had arranged her travel. The reason would soon be clear: The same day she crossed the border, her husband, Amedy Coulibaly, unleashed his terror spree in Paris, and she became the most-wanted woman in France.
No charges have been filed but authorities are eager to question Ms. Boumeddiene. “She is the prize—a high-value asset—because she knows a lot about the preparation of the attack,” said a counterterrorism official.
Her journey from the gritty suburbs of Paris to the Syrian border followed a circuitous route that—much like an underground railroad—allowed her to slip away covertly.