The call woke Detective Inspector Alex King at twenty past two in the morning. Uniform had been called to a house in Treforest, where it was reported a young woman had fallen from a rooftop. When Alex got there, the street was eerily quiet. The majority of the partygoers had already been sent home, though by all accounts clearing the scene had been pretty shambolic. Some had fled; others had stayed to gawp. Incidents such as this usually generated crowds of rubberneckers, people who longed for a glimpse of misery as an interlude in their lacklustre lives; a reminder that no matter how disappointing their own existence might be, some poor sod’s had just got a whole lot worse.

According to the call she’d received, there had been an outbreak of panic at the house on Railway Terrace, with many revellers fleeing as soon as they became aware of what had happened, while others gathered around the victim, arguing over what to do. The neighbours in the adjoining houses had been woken by the screams of eyewitnesses.

‘How many people were here?’ Alex asked the first of the two uniformed officers already at the house. He looked barely old enough to be out of school, and the sheepish expression that preceded his response was enough to answer the question.

‘We can’t be certain.’

‘Why not?’

The officer shrugged, which managed to irritate Alex more than any words might have done. ‘There was a houseful, apparently.’

The paramedics had pronounced Keira North dead at the scene. Her housemates were sitting in the living room, a girl and two boys, the three of them side by side on the sofa, stunned into silence. Alex glanced into the room as she passed, unable to ignore the chaos that surrounded the three students. A drink so blue it bordered on fluorescent had been spilled over the end of the beige sofa. Empty bottles and dirty glasses littered the flimsy self-assembly coffee table in the middle of the room. Evidently the party had been an eventful one long before its traumatic ending.

The girl had been crying; there were telltale signs of mascara smudged down her cheek and her skin was flushed with an assault of raw emotion. She was sitting nearest the door, her body turned at an awkward angle from the two boys beside her as though she was trying to block them out and pretend neither of them was present.

‘What sort of state are they in?’ Alex asked the officer, nodding towards the living room.

‘Not too bad now. The girl was pretty drunk when we first arrived, but the accident seems to have sobered her up.’

Alex followed the young officer through to the kitchen. The back door was open, leading out on to a small L-shaped area that passed as garden space. Like the inside of the house, the place was a mess. Smashed glass lay strewn on the patio slabs and cigarette butts adorned every available surface. There was evidence of drug use on the garden table.

She stepped into the yard. It was still warm out, despite the unearthly hour. Another man – the second of the two attending officers – was waiting there for her.

‘Scene-of-crime officers are on their way,’ she told him.

She studied the fallen body. The girl’s head was snapped back at an angle, her eyes still open. They stared past Alex’s shoes, unseeing, the life drained from the pupils. She was wearing a pair of black leggings and a short-sleeved checked shirt that had risen to her waist during the fall. Her long hair was tangled in messy tendrils across her back and face.

‘Why the hell has everything taken so long?’ Alex said, directing her impatience at the officers. ‘The call was made at just before midnight. Almost two and a half hours ago.’

She didn’t need to say any more; the unspoken accusation hung in the air between them. She stood with her hands on her narrow hips, her unnerving focus switching between the two men as she waited for some sort of response.

The second officer shot the first an uneasy glance. ‘It was chaos here. They had a houseful – we tried to get it cleared as quickly as we could.’

‘Cleared? Of what … witnesses?’ Alex shook her head and bit her tongue, saving the reprimand for later. ‘Show me the room.’

She and the first officer went back into the house. The young man showed her upstairs, to the bedroom that had been Keira’s and from which she had fallen. The room was neat and tidy, everything organised and in place. History textbooks lined the shelves above the closed laptop that sat on the desk. A dressing table stood to the side of it, make-up and hair products in orderly rows beneath the mirror. The bed was made, though indentations in the duvet suggested that more than one person had recently sat there.

Hanging above the bed was a photo collage; an array of images protected by clear plastic envelopes. Alex moved to the head of the bed and studied them closely. Many of the photographs had captured moments that had taken place in this house, and the faces she had seen downstairs in the living room were instantly recognisable. Then there were others: family, school friends; an accumulation of a young life’s worth of memories.

The word ‘accident’ echoed in Alex’s brain. Accidents could happen so easily, she thought. Misplaced footing, attention distracted by something or someone; it was easy to be caught off guard and end up suffering the consequences of a moment’s carelessness.

‘Anyone know what’s gone on here?’ she asked.

The broken glass on the carpet near the window indicated that something had happened in this room before Keira North had fallen to her death. It was a beer bottle, thrown against the wall; a splash of stains ran in streaks down the paintwork. Alex went to the window. She could feel the eyes of the young officer behind her, watching her every movement. If the looks that had been passing between him and his colleague were anything to go by, they both realised themselves guilty of a catalogue of errors.

‘We’re not sure. The three downstairs said they don’t know anything about it.’

Alex turned sharply. ‘Did you come up here?’ she asked. ‘When you got here?’

The officer hesitated on a response, which gave her the answer she needed.

‘How long did it take for one of you to get up here?’

The officer looked past her, to the still-open window. ‘Ten minutes,’ he mumbled. ‘Maybe fifteen.’

Alex’s reaction stamped itself on her face. Ten minutes was more than sufficient time for the scene to have been contaminated or altered. What had they been doing during that time, other than chasing off potential witnesses? She pursed her lips, trying to hold in her frustration. She would deal with the two of them later.

She turned back to the window. It was a large single pane of glass, side-opening. It swung into the room, allowing anyone inside to climb out on to what the students had apparently used as a makeshift balcony. It was clearly a breach of some sort of health-and-safety law. How tragic that it would take a young woman’s death for the landlord to do something about it. He or she would probably be facing charges too.

Careful not to touch the window, she leaned out to assess the space. The air was like stepping from a plane into a Mediterranean summer’s evening. There was a stillness; a stark contrast to the reported chaos of events just hours earlier. The cruelty of time, thought Alex. The world kept spinning, clocks kept ticking: time didn’t stop for anyone’s tragedy. Tomorrow the world would carry on as though Keira North had never existed.

There was a concrete ledge that ran the width of Keira’s bedroom, about nine feet long and a foot and a half wide. It led on to the sloping roof of the first-floor bathroom. It was from the ledge that Keira was reported to have fallen. What had she been doing there? It didn’t look obviously dangerous, although Alex imagined that any thoughts of safety had been easily abandoned under the fuggy influence of alcohol. The ledge was not wide enough to comfortably stand on, not without consideration of the drop below; at most, it could be used as a step between the window ledge and the bathroom roof. Partygoers reported having seen Keira sitting on the ledge earlier in the evening, and if that had been the case, Alex wondered how she had come to fall. Losing balance while drunk and standing was one thing; losing balance while sitting down seemed far less plausible, particularly given the angle and placement at which she had landed.

Alex drew back from the window. ‘Anyone with her when she fell?’

‘Her housemates say no.’

‘The three downstairs?’

The young officer nodded. They heard a noise at the front door. ‘SOCOs,’ Alex said. She gave the officer a nod and headed back out onto the landing. As she made her way to the first floor, she could hear the housemates talking downstairs in the living room, whispers that couldn’t be deciphered from her listening spot at the top of the staircase. When she went down further, her footsteps caused creaks on the stairs and the conversation came to a sudden stop.

She stopped at the living room. ‘You’ve all provided statements?’ she asked.

The three nodded, their movements so in sync that it looked almost as though they had been rehearsed.

Back out in the yard, a SOCO was crouched on the ground near Keira North’s body, tracking the area for clues. ‘Broken neck, you think?’ Alex said, as the woman looked up to greet her.

The woman nodded. ‘Good chance.’ She pointed to the roof of the first-floor bathroom. ‘Looks as though she hit the roof there before landing here. Must have been horrific to see.’

More horrific for the poor girl who was now lying at her feet, Alex thought.

She glanced at the yard around them and thought about the bedroom upstairs. Almost three hours had passed before this place had been properly treated as a crime scene. Potential witnesses had been left to walk away. If this turned out not to be a tragic accident, how much crucial evidence had been lost during that time? She looked back at the girl on the ground, and then at the scene-of-crime officers, trying to hold back the thought that this was all too little, too late.