‘You don’t trust anyone, Meera.’ He knew she had spent time on some of the capital’s poorest estates, in Peckham, Dagenham, Deptford, and Kilburn. It would be hard not to become cynical after a daily diet of gunshot wounds and stabbings committed in chip shops and at bus stops, where drug feuds were as liable to be settled at family weddings and christenings as on the street. Even so, there were days when she seemed barely able to contain her anger. ‘But if you did decide to trust someone,’ he said, ‘you could tell me anything.’

‘Thanks, Colin, but if it’s all the same to you I’d prefer to eat my own colon first.’ Her head lowered almost to the page as she returned to studying witness statements.

Be as nasty as you like, he thought. My back is broad. And I’ll persevere until the day I find out what makes you tick.

Next door, April rose from her dead computer screen and walked to the window of her office. The sky was animated with roiling clouds, dark and volatile, filled with glimpses of amber and emerald. The streets around the tube station were almost deserted. Camden was one of the most crowded, dangerous and interesting boroughs in London; the rush hour lasted around the clock and the pavements were never free of life, but there was something different about today. Raymond Land had come around telling everyone they were on paid leave for a week, but she could not trust herself to go home. Having conquered her agoraphobia with her grandfather’s help, she was loath to allow it the opportunity of returning within the confines of her safe, small flat.

‘Are you okay?’ John May stuck his head around the door. ‘May I come in?’

‘Of course.’ April still felt like an interloper at the unit, despite her involvement in an investigation that had finally closed a decades-old cold case. She knew there had been suggestions of nepotism, that she had only secured the job because she was the granddaughter of the unit’s cofounder, but she was already winning the trust of her colleagues, and the work was fascinating.

In the filing cabinets opposite were secret details of cases no other unit in the country had the ability to unravel. The PCU had earned the right to handle the kind of investigations no-one in the Metropolitan Police force had the faintest interest in solving. They had captured demons and devils, phantoms and monsters; not real ones, of course, mostly deluded loners who believed themselves invulnerable to the law. Individuals who had stolen, blackmailed and killed for tenebrous, private purposes, to protect themselves, to hide truths, to destroy enemies. Murder, Arthur Bryant insisted, was invariably a squalid, sad business driven by poverty and desperation, yet the cases passed to the Peculiar Crimes Unit had often been marked by paradox and absurdity. Sometimes they were the dream cases other detectives fantasised about resolving, but Bryant and May chose their staff with care, employing novices who were knowledgeable social misfits, in the same way that computer companies sometimes hired the very hackers who had attacked their clients from behind bedroom doors.