Beth Farlow waved at the security guard on duty behind the glass in reception at the end of a long shift. Everyone who came or left Ryegrove Hospital went through the same checks, like airport security. They weren’t just screened for sharp objects; they weren’t allowed phones, money, glass, computers, maps of the area, chewing gum or string. The guard, Jack, was busy checking a video display but he generally made time to talk to Beth, and she was always genuine in return.

At twenty-four, Beth was doing what she’d always wanted to as a staff nurse, and not even the repetitiveness of the security check could dampen her spirits. When she explained to people that she nursed in a secure mental health unit, it not only stopped conversations, it generally made people’s faces twist in incredulity. Something about the way she looked, and her personality, made them think of paediatrics or a care home assistant when she said she was a nurse. But that was just her surface coating. Underneath the smile burned a bright and sharp commitment to mental health, the least glamorous of all the NHS services. Beth liked making a difference. As part of the Forensic Services division of the North Bristol NHS Trust, she worked providing care and treatment for a client group with learning disabilities and personality disorders, who displayed ‘serious irresponsible behaviour’ – which was a deliberately broad term. Her patients – she hated the word clients – were murderers and rapists and people whose views of the world, and of themselves, were very badly skewed.

She’d been lucky to get the job and even luckier to have found a room in a house in Severn Beach, shared with one of her old college mates, Dee, on the nursing degree course at the University of the West of England. It was way too far out of town, but it was quiet and cheap because the house – more a cottage if truth be told – had once been owned by Dee’s grandmother. Beth took the train in and out of the city to work and cycled the final mile from Severn Beach station to the cottage on the edge of what once had been a farm.

She joked that it was keeping her fit.

From her cottage bedroom she could see the river and the Severn Crossing, and opposite the property was a wild wood. Because most of the traffic hissed by above them, it was surprisingly quiet, and two or three nights a week, she had the place to herself with Dee over at her boyfriend’s.

It was almost six thirty when she got off the train. The station emptied quickly, and Beth walked outside, pulling on her gloves and reaching for the key to unlock her bike. If Dee was home and not sleeping, she’d come and pick Beth up, but today was not one of those days. Thank God it wasn’t raining. She reached for the key to unlock the chain that held her bike to the rack. Her helmet was in the pannier on the back and she slid it on. People were hurrying to their cars or their homes. In ten minutes she’d be at the cottage: a nice warm meal, a little TV, bath and bed. She looked up at the road and the lights of the Severn Crossing in the distance and felt the little twinge of anxiety that had been her unwelcome companion these last few nights. Something about this final leg of the journey, one she’d made dozens of times, had begun to unnerve her. She wasn’t even sure why.

Just get on with it, then, sensible Beth muttered. It’s keeping you fit, remember?

On a dark and freezing February night, all Beth wanted to do, like everyone else, was get home. She shrugged and wished it wasn’t quite so far and quite so cold and quite so winter dark.