They parked the car in a bay a short distance further along, then ran back through the rain, Emma-Jane holding the large brown envelope over her head, and in through the front door of the premises – which set off a bell with a loud ping.

The smell hit Grace instantly: a sharp, intensely sour reek, toned down just a fraction with sawdust. They were in a dimly lit area, completely surrounded, floor to ceiling, by cages with ultraviolet back-lighting, inside some of which he could see insects crawling around. He peered into one cage, only inches from where he was standing, and saw a pair of brown antlers twitching. A very large beetle, too large and too close for his comfort. He took a couple of steps back, wiped away some rainwater from his brow and gave the DC a What the hell is this place? frown.

Then he saw the spider, or rather its yellow and black hairy leg, followed by another leg, then another; it moved across its cage in three fast darts. It was enormous; with its legs outstretched and plainly visible now, the thing would not have fitted on a dinner plate.

Emma-Jane was watching it also; she looked very uncomfortable. Which was how he felt. The more he looked around, the more tiny eyes and twitching antennae he saw. And the stink was nearly making him retch.

Then an internal door opened, and a short, thin man in his late forties emerged, wearing brown overalls and a white shirt done up to the top button, but with no tie. He had small, wary eyes beneath massive, bushy brows that looked like two warring caterpillars. ‘Can I help you?’ he asked in a reedy voice with a tone that was distinctly aggressive.

‘Are you George Erridge?’

His response was very hesitant and drawn out. ‘Ye-es.’

‘I’m Detective Constable Boutwood,’ E-J said. ‘We spoke yesterday. This is Detective Superintendent Grace from Brighton CID.’

Grace held up his warrant card. The man peered at it, seeming to read every word, his face twitching, his eyebrows going hammer and tongs at each other. ‘Yes,’ he said. ‘Right.’ Then he looked at the two police officers in expectant silence.

E-J removed a colour photograph from the envelope and handed it to the man. ‘We’re looking for someone who might have supplied this creature to a customer in England.’

George Erridge gave the photograph just a brief glance and said almost instantly, ‘Copris lunaris.’

‘You import tropical insects?’ Grace asked.

The man looked quite offended. ‘Not just tropical; European, pan-Asian, Australian; from all over the world, really.’

‘You might have imported this one?’

‘I usually keep some stock. Would you like to see?’

Grace was tempted to say, No, I really would not, but instead said dutifully, ‘Yes, I would.’

The man led them through the internal door he had emerged from, into a shed a good hundred feet long. Like the shopfront, it was lined floor to ceiling with cages; the smell was even worse in here, much more sour and pungent, and the lighting just as dim.

‘This is the roach room,’ Erridge explained with a tinge of pride. ‘We supply a lot of these to the pharmaceutical industry for tests.’

Grace, who had always had a loathing for cockroaches, stopped and peered into one cage in which there were about twenty of the brown creatures. He shuddered.

‘One of the most resilient animals on the planet,’ the man said. ‘Did you know that if you cut off a cockroach’s head, it can live for up to fifteen days? It will still keep going back to its original source of food. Won’t be able to eat it, of course.’

‘Yech!’ Emma-Jane gulped.

‘I didn’t know that,’ Grace said. Thanks for sharing it with me, he nearly added.

‘They would survive a nuclear holocaust. They finished evolving hundreds of thousands of years ago. Doesn’t say much about the human race, does it?’

Grace looked at him, uncertain how to reply. Then he and E-J followed him through another internal door into an even longer shed. Halfway down, George Erridge stopped and pointed at one small cage. ‘There you go,’ he said. ‘Copris lunaris.’

Roy Grace looked for some moments before he saw one of the beetles with its distinctive markings, motionless.

‘So, if I might ask, what exactly is your interest in these beetles?’ Erridge said.

It was so tempting to tell him, and watch his expression, that Grace had to fight hard to restrain himself. ‘I can’t tell you the circumstances, but one of these beetles was found at a crime scene. What we would like from you is a list of any of your customers who have bought one of these from you recently.’

George Erridge went quiet, but his eyebrows jigged furiously at each other. ‘I’ve only had one customer in recent months. Not much call for them, really; just the occasional collector and new museums – don’t get many of those.’

‘Who was the customer?’ Grace asked.

Erridge dug his hands into his overall pockets, then pushed his tongue hard against his lower lip. ‘Hmmn. Funny bloke, sort of eastern European accent. He rang me ’bout two weeks ago, asking very specifically if I had any Copris lunaris in stock. Said he wanted six of them.’

‘Six?’ Grace said, horrified. His immediate thought was Six murders like this one? ‘Yes.’

‘Alive or dead?’

Erridge looked at him strangely. ‘Alive, of course.’

‘Who do you normally supply to?’

‘Like I said, the pharmaceutical industry, natural history museums, private collectors, film companies sometimes; supplied a tarantula recently for a BBC production. I’ll tell you a trade secret: insects are a lot easier to control than other animals. You want a docile cockroach, just put him in the fridge for four hours. You want an aggressive cockroach, put him in a frying pan on low heat for a few minutes.’

‘I’ll remember that,’ Grace said.

‘Yes,’ Erridge replied intensely seriously. ‘That’s what you need to do. They don’t suffer, you see. They don’t feel pain the same way we do.’

‘Lucky them.’

‘Indeed.’

‘What details do you have of this man who bought six of these?’ Emma-Jane asked.

Looking a little defensive, Erridge said, ‘I don’t have any details. I only keep records on my regulars.’

‘So you hadn’t dealt with this man before?’ she asked.

‘No.’

‘But you met him?’ Grace asked.

‘No. He phoned up, asked if I had them, and told me he would send someone to collect them. He sent a minicab and the driver paid cash.’

‘A local firm?’

‘I wouldn’t know. I don’t use minicabs; can’t afford ’em.’

Grace’s mobile phone suddenly beeped then vibrated. Excusing himself, he turned away from the insect expert and answered it.

‘DS Grace,’ he said.

It was Branson. ‘Yo, old man,’ he said. ‘How you doing?’

‘I’m shopping,’ Grace said. ‘Buying your birthday present. What’s up?’

‘The bloke who rang me during the briefing – the paranoid one I had to speak to in the phone booth who said he thinks he witnessed information about Janie Stretton’s murder?’

‘Uh huh,’ Grace said.

‘He said he saw it on his computer after inserting a CD he found on a train.’

‘Is he letting us have a look at it?’

‘I’m working on that now.’