‘Is this the only way up to the roof?’ Kim asked, as they mounted stone steps from the third floor via a corridor that ran behind a row of bedrooms.

Brendan Thorpe shook his head. ‘There’s a fire escape in the West wing but that’s been closed off to the roof for more than a year now,’ he said, taking a set of keys from his pocket that hung lower than it would have done if his trouser belt had been working more effectively rather than sitting beneath the middle-aged paunch.

He tried the door first to find it locked.

‘Could Sadie have got a spare key from anywhere?’

Thorpe looked puzzled. ‘I don’t see how,’ he said, frowning.

‘Well, she got up here somehow,’ Kim observed, in case he’d forgotten there was a dead teenager on the ground. The girl’s purloining of the key was about to be the least of his problems.

‘I’m sorry, Inspector, you’ll have to bear with me, I’m still in a little bit of shock,’ he said, trying the wrong key.

‘I understand that, Mr Thorpe, but it would be useful to know how many roof keys are in existence.’

‘Of, course,’ he said, as they stepped outside.

‘There is one on my master set, the deputy principal has an identical set to mine. The janitor, the maintenance crew, each housemistress or master has a reduced set of keys, which includes a roof key.’

‘So, that makes?’ Kim prodded.

‘A total of fourteen roof keys,’ he answered.

Kim glanced at Bryant who took out his notebook.

She stepped outside onto the flat roof and looked around assessing the scale of the buildings joined together by walkways and ladders. From where she stood Kim could make out four clear wings, each the size of a couple of football pitches. Navigating the area from up here would be challenging enough, but downstairs, spread over three floors, she’d need a decent satnav to get her around the school.

She stepped over a roof light and around an air conditioning unit to head towards the area she thought was the side of the building.

Thorpe’s phone began to ring. ‘Please, excuse me,’ he said, edging back towards the stairwell.

Bryant joined her on a patch of recently repaired bitumen.

‘My apologies, Inspector. I have to go,’ Thorpe said, gravely. ‘Sadie’s parents are at the police cordon.’

‘Do they know?’ Bryant asked.

He shook his head. ‘Only that there’s been an incident.’

Kim understood. Delivering such news over the phone was only done as a last resort. She did not envy him his next job.

‘We’ll let you know when we’re done,’ she advised as he re-entered the building.

Bryant shoved his hands into his trouser pockets as he stood beside her.

She narrowed her eyes at him when he started humming the Ghostbusters theme.

‘Just look down there,’ she said.

‘Must I?’ he asked, taking a tentative step forward.

Three storeys below lay the body of Sadie Winters, guarded by uniform officers while others worked to take details and clear the area. Keats had arrived, accompanied by his team of crime scene techs, who were changing into white protective suits.

‘You think she jumped from here?’ Kim asked, lining herself up with the body on the ground.

Bryant nodded and stepped back. ‘Yeah, seems about right.’

‘Hmm…’ she said, taking five steps to the left.

‘Was that the wrong answer?’ he asked.

‘How about here?’ she asked, ignoring his question.

Again, he took a cautious step forward and shook his head. ‘Too far away.’

She walked past him and headed to the right.

‘How about here?’ she asked.

‘Guv, are you trying to make me throw up?’

‘I haven’t cooked for you in ages, now just look,’ she urged.

He looked down and shook his head. ‘Much too far away from where she landed,’ he said.

She returned to her first position which was directly in line with the body. She frowned as she looked down.

‘Who you gonna c— aah, I think I see what you’re looking at,’ he said.

‘The railings,’ she clarified.

A row of black wrought-iron spikes, about four feet high, surrounded a narrow-planted area she’d noticed on the ground. Four steps either way and there were no railings.

‘It’s obstructive,’ Kim said. ‘You look down and picture your body landing on those spikes.’

‘Ugh,’ Bryant said, looking away.

‘Exactly,’ Kim said. ‘And you’re a fully grown adult… allegedly.’

‘But if I’m killing myself anyway I’m expecting a broken neck or a fractured skull?’ he argued.

‘But do you really want to picture yourself impaled on those spikes?’ she asked.

‘Not really but I’m not a troubled thirteen-year-old girl,’ he offered.

‘Yeah, but I was, and I can tell you that I would have noticed those spikes.’

People wanted to die painlessly and that was no different for suicides. Fast and painless. Logically, it didn’t make sense to her. She recalled the grey mark on the bottom of Sadie’s shoe as she took another look around the surface of the roof.

‘Hmmm…’ she said, not finding what she sought.

‘What now?’ he asked, wearily.

‘The cigarette,’ she answered. ‘Sadie had recently ground out a smoke with her shoe but there’s no cigarette butt here,’ she observed.

‘Guv, what exactly are you thinking?’ he asked, with a note of fear in his voice.

‘I’m thinking we might just have a chat with our good friend Keats before we leave.’