Gloved hand on the banister, she climbed the rest of the stairs, almost knocking off a notebook and a USB stick that were balanced on the post at the very top. Strange place to keep them.

When they were both upstairs, Pip studied the various doors that opened on to the landing. That back bedroom on the right couldn’t be Andie’s; the floral bedspread was ruffled and slept in, paired socks on the chair in the corner. Nor could it be the bedroom at the front where a dressing gown was strewn on the floor and a glass of water on a bedside table.

Ravi was the first to notice. He tapped her gently on the arm and pointed. There was only one door up here that was closed. They crossed over to it. Pip grasped the gold handle and pushed open the door.

It was immediately obvious this was her room.

Everything felt staged and stagnant. Though it had all the props of a teenage girl’s bedroom – pinned-up photos of Andie standing between Emma and Chloe as they posed with their fingers in Vs, a picture of her and Sal with a candyfloss between them, an old brown teddy tucked into the bed with a fluffy hot-water bottle beside it, an overflowing make-up case on the desk – the room didn’t feel quite real. A place entombed in five years of grief.

Pip took a first step on to the plush cream carpet.

Her eyes flicked from the lilac walls to the white wooden furniture; everything clean and polished, the carpet showing recent vacuum tracks. Dawn Bell must still clean her dead daughter’s room, preserving it as it had been when Andie left it for the final time. She didn’t have her daughter but she still had the place where she’d slept, where she’d woken, where she’d dressed, where she’d screamed and shouted and slammed the door, where her mum whispered goodnight and turned off the light. Or so Pip imagined, reanimating the empty room with the life that might have been lived here. This room, perpetually waiting for someone who was never coming back while the world ticked on outside its closed door.

She looked back at Ravi and, by the look on his face, she knew there was a room just like this in the Singhs’ house.

And though Pip had come to feel like she knew Andie, the one buried under all those secrets, this bedroom made Andie a real person to her for the first time. As she and Ravi crossed over to the wardrobe, Pip silently promised the room that she would find the truth. Not just for Sal, but for Andie too.

The truth that could very well be hidden right here.

‘Ready?’ Ravi whispered.

She nodded.

He opened the wardrobe on to a rack bulging with dresses and jumpers on wooden hangers. At one end hung Andie’s old Kilton Grammar uniform, squashed against the wall by skirts and tops, no room to part even an inch of space between the clothes.

Struggling with the rubber gloves, Pip pulled her phone out of her jeans pocket and swiped up to turn on the torch. She got down on her knees, Ravi beside her, and they crawled under the clothes, the torch lighting up the old floorboards inside. They started prodding the boards, tracing their fingers round the shape of them, trying to prise up their corners.

Ravi found it. It was the one against the back wall, on the left.

He pushed down one corner and the other side of the board kicked up. Pip shuffled forward to pull up the floorboard, sliding it behind them. With her phone held up, Pip and Ravi leaned over to look inside the dark space below.

‘No.’

She moved the torch down inside the small space to be absolutely sure, pivoting the light into each corner. It illuminated only layers of dust, gusting out in whirlwinds now because of their picked-up breath.

It was empty. No phone. No cash. No drug stash. Nothing.

‘It’s not here,’ Ravi said.

The disappointment was a physical sensation gouging through Pip’s gut, leaving a space for the fear to fill in.

‘I really thought it would be here,’ he said.

Pip had too. She thought the phone screen would light up the killer’s name for them and the police would do the rest. She thought she’d be safe from Unknown. It was supposed to be over, she thought, her throat constricting the way it did before she cried.

She slid the floorboard back in place and inched backwards out of the wardrobe after Ravi, her hair getting briefly tangled in the zip of a long dress. She stood, closed the doors and turned to him.

‘Where could the burner phone be then?’ he said.

‘Maybe Andie had it on her when she died,’ Pip said, ‘and now it’s buried with her or otherwise destroyed by the killer.’

‘Or,’ Ravi said, studying the items on Andie’s desk. ‘Or someone knew where it was hidden and they took it after her disappearance, knowing that it would lead the police to them if it was found.’

‘Or that,’ Pip agreed. ‘But that doesn’t help us now.’

She joined Ravi at the desk. On top of the make-up case was a paddle hairbrush with long blonde hairs still wound round the bristles. Beside it, Pip spotted a Kilton Grammar academic planner for the year 2011/2012, almost identical to the one she owned for this year. Andie had decorated the title page of her planner under the plastic with doodled hearts and stars and small printouts of supermodels.

She flipped through some of the pages. The days were filled with scribbled homework and coursework assignments. November and December had various university open days listed. The week before Christmas there was a note to herself to maybe get Sal a Christmas present. Dates and locations of calamity parties, school deadlines, people’s birthdays. And, strangely, random letters with times scribbled in next to them.