The sound, muted but insistent, fractured the early morning quiet. I followed the gulp-croak, gulp-croak into the front hallway in time to place a towel under my vomiting dog’s muzzle. It was four-thirty in the morning. I could hear the churning of his intestines. He looked at the front door.

January had just begun and the sun wouldn’t be up for two hours. Only a foolish woman, featherweight and middle-aged, accompanied by no one other than a small, friendly dog would head into the dark urban...