“Could I pass for a boy?” I asked. The black skirt of my abaya still trailed the floor, but from the waist up I felt pretty pleased with the effect.

Fahad, the most talkative of the boys, snorted.

“No,” he said. “But I think that’s as good as we’re going to do. We’re going to put you in the middle seat, and if you see someone in another car staring, turn slowly away.”

We piled into the S.U.V., and Thamer clicked through a rap mix CD to find Akon’s “Smack That,” to set the right mood for an evening of numbering. The boys bobbed their heads in time to the music.

“Wanna jump up in my Lamborghini Gallardo/Maybe go to my place and just kick it, like Taebo?” Akon sang.

In reality, getting a girl to go anywhere with him, let alone to “kick it,” is a near impossibility, Fahad explained. For most young Saudi men, a night of numbering is simply a night driving around with friends, listening to music, chasing cars containing black-draped figures that could just as easily be old women as young girls. Since numbering is considered harassment, detention by the religious police is an ever-present possibility.