Chase, of course, could sprint up the trail. Lily gave a fair showing, and by the time she reached the small circle of people standing around a young man and woman kneeling over a prone figure in khaki pants, boots, and a green T-shirt, Chase had the backpack open and was pulling out emergency supplies. She set a battery-powered lamp on the ground that added to the eeriness of the scene by illuminating the key figures in harsh white light while the surrounding forest receded into ominous gloom.

Taking a deep breath to steady her mind, Lily knelt next to a dark-haired young man who looked to be in his midtwenties who was doing chest compressions. Sweat streaked his face, leaving thin dusty rivulets down his cheeks. A woman about his age and half his size kept the unresponsive man’s airway open with her fingers supporting his flaccid lower jaw. From the sheen of sweat on her face, the two of them had probably been alternating compressions, a back-breaking and exhausting physical undertaking.

“I’m a doctor,” Lily said, thumbing open the latches on the med box. At a quick glance, the male patient appeared to be in early middle age—somewhere around forty—and fit looking. She saw no immediate signs of trauma to suggest he had fallen from any great height. All four extremities lay in a natural position with no evidence of blood loss on his person or the surrounding ground. His eyes were closed, his skin tinged a faint blue gray. She pressed her fingers to his neck and felt a faint pulse of blood each time the student compressed his chest. “What’s the situation here?”

“We were a hundred yards up the trail,” the young woman said, her voice tight but steady, “when we heard a man shout for help. We got here within twenty seconds, probably, and this gentleman was on the ground. He did not appear to be breathing, did not respond to commands, and we could not find a pulse. We immediately began CPR.”

“Good. Did anyone with him know anything about his medical status?”

“I-I don’t know. We didn’t—I didn’t ask.”

Lily called, “Chase, can you get the leads on?”

“Right here.” Chase leaned down, pulled a big pair of bandage scissors off her belt, and slit the man’s T-shirt down the middle. As she positioned the EKG leads and defibrillator pads, she said, “He was hiking alone, apparently. The guy who yelled for help just told me he came around the bend and saw this guy on the ground.”

Lily grimaced. “He didn’t see him fall?”

“No.”

“So we don’t know how long he’s been down.” She looked at Chase, whose grim expression matched what she was feeling. “Anything?”

Chase looked at the EKG readout and shook her head. “Flatline.”