Two days later, after working a long shift at the hospital, Beth dressed for a run. Marcus had neither said nor done anything unusual since their dinner conversation: no flirting, no gestures, no offer to talk further. He was difficult to read. Beth tried to take her mind off the odd vibe between them, but it wasn't easy. She thought a vigorous run might help as she donned her shoes, shorts, and tank top.

She began doing calf stretches against the wall and winced at a stitch in her thigh.

"Something wrong, Mom?" Marcus asked.

"Just a cramp in my leg," she said. "I'll work it out."

"Let me help."...