Michelle pulled her coat tighter around her neck as she left the hospital for the night and headed into the brisk D.C. fog. It had been a long shifttoo long. She couldn't sustain work hours like this, and a talk with her boss was long overdue.

Maybe she shouldn't have switched hospitals. She now had the least amount of seniority of anyone in the department, and that meant she worked nights, weekends, and holidays. She'd taken for granted being able to pick and choose. She'd been dazzled by the promise of a signing bonus, along with an increase in pay.

Michelle tried to think of other things as she walked quickly down the street. The blue light of television sets flickered behind a few drawn curtains, but most of the windows were dark. Reasonable people with reasonable bosses had already gone to bed.

The images of the day kept flashing through her mindthe endless flow of patients, the suffering, the impatient doctors, the results she knew would be bad news to be delivered to patientsand she shook her head vigorously as if she could shake the thoughts free.

No more. She'd think about all that tomorrow.

She tried to think of happier things. Of the frozen meal awaiting her at home, of a night of comedy reruns, a glass of chardonnay big enough to swim in. Separating work from her life was getting to be a harder and harder endeavor.

The noise snapped her out of it.

She looked around quickly, her skin crawling at the sudden sound, and saw only an empty street behind her. Parked cars lined the narrow avenue, but she couldn't see anything else in the darkness and fog.

Too late. It was too late to be going home this time of night. She glanced at her watchnearly 11. She chided herself. She had meant to leave at 7. Again.

Michelle increased her pace. Home was only a few blocks away now.

But then, it came again. The noise.

She stopped again. Michelle peered through the fog in the dim streetlight.

Hello? she called, her voice trembling. She was so close to home now. She didn't need this. It wasn't any of her business. She kept on walking, calmly and purposefully, as if she hadn't heard anything.

But she had.

The noise hadn't come from a car. It was too sharp. She heard it again. A sharp, short crack. It didn't sound like a gunshot, either. So what was it?

She walked faster.

It was coming from somewhere behind her. What if someone was hurt? What if they needed help? What if she switched on the news tomorrow and saw that someone she could have helped had died, right here, a few blocks from her apartment?

Michelle stopped in her tracks. She turned around.