Alex pulled up outside the student house on Railway Terrace. The street looked different in daylight: wider and dirtier, the buildings neglected and the air permeated with a tinge of grey despite the burst of summer sunshine fighting through the clouds overhead. She glanced in the rear-view mirror. David and Louisa North had parked up behind her. She could see Louisa in the passenger seat, staring blankly at the house in which her daughter had died just two days earlier.

‘Here goes,’ Alex said to herself, reaching for the door handle.

She was still disappointed by Harry Blake’s response to the case. Scene-of-crime officers had attended the house in the early hours of Monday morning, but only after hours had already passed. The mistakes made by the first attending officers meant the building hadn’t been searched thoroughly. Before the first signs of daylight, the young woman’s death had been all but pronounced an accident by most. Superintendent Blake agreed, and Alex wasn’t sure he would allow her sufficient time to prove otherwise.

She only hoped the others living there had had the common sense not to go into Keira’s room and touch any of her things. The girl’s parents had already endured enough. Tom Stoddard hadn’t struck Alex as the most sensitive of individuals, although why he’d want to go into Keira’s room following her death, she didn’t know. Unless there was something he was trying to hide.

The three housemates had been told when the police and Keira’s parents would be visiting the house and had been asked to make sure they were out before they arrived. The last thing David and Louisa needed was the reminder that other young people – people whose everyday existences had intertwined with that of their daughter – were continuing their lives without disturbance.

As Alex got out of the car, Louisa and David stepped from their BMW and waited tentatively at the kerbside, as though reluctant to go any nearer the house.

‘I’ve got some suitcases in the boot,’ David said. ‘Can I bring them in?’ His voice was uneven, trembling.

Alex nodded.

‘We’ll just collect her clothes and things,’ he added unnecessarily, seemingly desperate to break the unnerving silence. ‘Someone will need to sort through them.’

Louisa North’s top teeth were clamped on to her bottom lip, fighting back an onslaught of angry tears. She looked at the pavement, avoiding eye contact. Whatever was to come next, Alex thought, was going to be noisy and ugly and cruel. Grief was relentless but unpredictable. Though some sort of reaction was inevitable, how it would manifest itself could never be anticipated. Once they got inside the house, they were going to have to go through it with her.

She took one of the suitcases from David and led the way to the front door. It was quiet inside, almost unnaturally so. She noticed something else: it was a different house to the one she had visited in the early hours of Monday morning. The place was spotlessly clean and the air smelled of some kind of plug-in fragrance. The carpets had been vacuumed and the junk that had littered the stairs – piles of envelopes and discarded bags and jackets – had all been cleared away.

When she glanced into the living room, it was barely recognisable as the room in which she had interviewed Keira’s three housemates. The lurid blue stain on the sofa had disappeared – either cleaned away or concealed by turning the cushion over – and there was no trace of the debris that had cluttered the room. As everywhere else, the place had been polished and vacuumed.

They had gone to quite an effort, Alex thought. For whose benefit?

David North was standing at the foot of the stairs, clutching the second suitcase to his chest. Louisa had hung back, still lingering by the door as though uncertain of whether or not she really wanted to go any further.

‘Have you been here before?’ Alex asked.

David nodded. ‘September, when she moved in.’

‘Let’s take these to her room.’

She led the way soundlessly up the stairs, David and Louisa following. On the second floor, they went to the bedroom at the back of the house. It was as though time had stopped there. Though officers had since searched the room, things were still exactly as Keira had left them: a pair of pyjamas folded and placed on the pillows at the head of the bed; the book she had been reading still resting on the bedside table, its spine bent at the last page she’d seen.

Alex considered the nature of Keira’s room and her possessions. They weren’t those of an average student. There was a multitude of clothes in her wardrobe, all fashionable and with labels from the pricier end of the high street. If her parents’ car was anything to go by, the North family wasn’t short of money.

David North moved into the room like a ghost, his face fixed with an expression of hopelessness. Alex placed her suitcase on the floor, careful not to disturb anything.

‘If you need me,’ she said, ‘I’ll be downstairs.’

When she turned, she saw Louisa staring at the window. The woman didn’t acknowledge her as she passed.

She headed down to the first floor and stood in the open doorway of one of the boys’ bedrooms. Something wasn’t right. She had never seen this room before, but she very much doubted that this was its usual state. There were no dirty clothes on the floor, no mugs or plates left lying around: all things she might have expected from the bedroom of a student. It was too tidy; too organised.

She moved further into the room, browsing the few textbooks that lined a shelf on the far wall. This room was Tom’s rather than Jamie’s: there were neat piles of university work, and Alex recognised the trainers he’d been wearing when they’d interviewed him the day before.

Anything that might be used as evidence had already been collected, so there was now no reason why the students shouldn’t have tidied up. Maybe they had done it out of respect for Keira’s parents. She raised an eyebrow at the thought. She’d been fairly cynical as a younger woman; now, at the age of forty-four, Alex looked for the ulterior motive in everything and everyone. It wasn’t the best way to live, she knew, but life had done little to discourage the habit.

She stood with her arms folded across her chest, taking in the orderliness of the room. She felt a weight of pressure upon her. Someone had pushed Keira from that window ledge, she felt certain of it. There were two people upstairs who deserved the truth. At this moment, the responsibility to unearth that truth seemed to be hers and hers alone.

There was something about Tom Stoddard she didn’t like and didn’t trust. His housemate had died, yet he had seemed so nonchalant when he had been interviewed; so uninterested in finding out what had happened to Keira. Leah and Jamie had both cried during their interviews with the police, in mourning for the young woman they had considered a friend as well as a housemate. Tom’s removal from what had happened seemed alien to Alex; she suspected that either he was emotionally defunct, or there was another more incriminating reason for his strange behaviour.

Her thoughts were interrupted by the sound of raised voices from the floor above. She went back out onto the landing, heading back up to Keira’s room. When she got there, she found Louisa North outside the window, sitting on the ledge where her daughter had spent her final moments. Her husband was leaning out of the window, trying to coax her back into the room.

‘Louisa, stop this, please.’

Alex raised a hand, signalling for him to stay calm. She had no idea what Louisa was doing, but anything was possible. They’d only seen the edges of her grief. There would be stages now – awful, seemingly relentless stages of sorrow that would drag this couple through the worst times their lives would ever likely have to endure – and what they were witnessing was merely the beginning.

‘Louisa,’ she said quietly, careful not to sound panicked by the woman’s erratic behaviour. ‘Can you come back in so we can talk?’

Louisa batted her husband’s hand away before turning to come back through the window. ‘You think I’m going to throw myself off the roof?’ she said, her voice laced with scorn. ‘Now? With my daughter’s killer to find?’

The words were like a slap to David North’s face. Tears sprang forth, his watery eyes contrasting with the pale lifelessness that had fixed itself upon his wife’s face.

‘She didn’t fall from the ledge, did she?’ Louisa said through gritted teeth, avoiding eye contact with them both. ‘Someone killed my daughter.’