Zoey Ramirez stared unblinking at the ambulance racing ahead of her and said a silent prayer that the girl inside it was alive. If anyone had told Zoey two hours ago that she would care at all if Audra Wilson lived or died, she would have thought they were nuts. Two hours ago she had no idea this was going to happen.

Squeezing her eyes shut, Zoey tried to block out the lights and sirens flashing and screaming around her, the metal grate between her and the two police officers in the front seat, and the realization that this was usually a seat for criminals. The wailing siren on the roof of the car made her head ache. In the darkness behind her eyelids, images flickered – a horror movie, the one she was living.

Zoey cringed at the scenes playing over and over in her mind. The argument on the bridge. The crazy look in Audra’s eyes. Audra lunging at her. The chilling realization that her life was in real danger – and the quick step to the side that had sent Audra plummeting over the edge. Again, Zoey heard Audra’s crazy laugh. Again, she felt her hand closing on air, and saw Audra’s body slip beneath the white water. It had all happened so fast. It just didn’t seem real.

After the fall, Zoey had felt like she was on autopilot. Clutching her useless cell phone, she’d started running. She ran until the tiny screen finally registered a signal, then dialed 911. Everything after that had been a blur of questions and sirens and adrenaline. She was still in that blur.

Zoey opened her eyes as the police car pulled up beside the ambulance at the emergency-room entrance of Silver Spring General Hospital. The driver turned off the sirens but left the lights flashing. Zoey craned her neck to see what was happening. She reached for the handle of the door, but found there was none. She was trapped in the police car, trapped in a nightmare. Pressing her forehead against the cold glass, Zoey watched as several medics rushed out of the emergency entrance toward the opening doors of the ambulance. They shivered in their scrubs, wrapping their arms around themselves to keep warm in the sharp autumn air. In some far-off spot in her mind, Zoey realized she was shivering, too, from shock and fear.

Zoey watched as the EMTs unloaded a metal gurney from the ambulance – the gurney bearing Audra’s body. Catching a glimpse of Audra’s dark, wet hair, Zoey’s stomach twisted again. This was not some movie she was watching or some dream she would wake up from soon. This was real. Zoey looked away as the medics rushed the gurney inside, shouting to one another in hospital code.

The officer in the driver’s seat got out and opened Zoey’s door. “Let’s go,” he barked. Zoey felt like a criminal. If only she hadn’t gotten into Audra’s car. If only she’d caught Audra’s hand. If only...