"A male is beating a female between two buildings," the dispatcher says. "13th and Lehigh."

It's just past 2 a.m. on a Friday night, and police officer Dennis Stephens, a 16-year veteran, is two hours into his shift patrolling North Philadelphia's 22nd District. So far, the night has been quiet, but now the bars are letting out, and things are starting to heat up. Stephens flicks on the squad car's lights and siren. He hits the gas. Here we go.

We charge down Lehigh Avenue, barreling through red lights, hitting over 60 miles per hour, which may be nothing on a highway, but on a city street is like riding a rocket ship.

We pull up to the intersection of 13th and Lehigh. But there's a problem: No victim. No perpetrator. No witnesses. Stephens looks between all the buildings. He searches a nearby parking lot. He circles the block. He'd ask people if they saw anything, but there are no people out here at all.

"If it's going to be anywhere, it's back here," Stephens says, turning the car into a dark, narrow pathway that is Oakdale Street. "They usually drag the hookers back here." He shines the headlight attached to his door into a concrete alcove that's nestled behind a crumbling house. It is a place that whispers Bad things have happened here. It, too, is empty.

Finally, he gives up. Elapsed time since he took the call: about 20 minutes. Effect on the city's homicide crisis: probably none. Percentage of 911 calls that turn out like this one: more than you think.

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