A boy that looked like he wasn't old enough to drive shoved past her. She dropped the plastic bag as his foot pulled it from her hand. The clothes didn't give him enough purchase on the next step to get the angle he wanted. His ankle went one way and his body went the other. His head was destined for the concrete stair and I thrusted the rugged suitcase under his chest. He didn't crack his head open but he looked more like a pretzel than a person when he came to rest.

Meanwhile, a second kid cleared the plastic bag, the stairs, and his friend. He was headed directly...