Chris wiped the sweat from his forehead as he jogged along the winding path through the park. The sun beat down on his t-shirt, making it stick to his chest. He was in his mid-twenties, fit from regular runs, with short brown hair and an easy smile. Today, he felt good, his legs pumping steadily over the dirt trail lined with tall trees and thick bushes.

Not far behind on a crossing path, Lily ran at her own pace. She was twenty-three, with long blonde hair tied in a ponytail that bounced with each step. Her sports bra and shorts hugged her curves, and she loved the freedom of running...