'You can't blame him, boss. You wouldn't give out information to someone who called you at home, would you?'

Bolt sighed. 'We're going to have to get his address and drive up there.'

'We could arrange for local CID to go round there if we told them what we needed to know. It would save us a long journey.'

Bolt looked at his colleague. There were big black bags under his eyes and he looked shattered. 'I'd rather do it myself, but there's no need for you to come with me. Honestly. I can drop you back home on the way. It's different for me. It's personal.'

Mo frowned. 'I was never a major fan of Tina Boyd, boss, but I still want to find her. And I want Hook just as much as you do. I worked the Leticia Jones case as well, remember?'

'I just thought maybe you could do with the rest. You look pretty whacked out.'

'I am. But look in the mirror. You do, too. We're in this together, boss. And also, there's still the matter that you saved my neck tonight, whatever you might think. So I owe you. Make the most of it. It won't last for ever.'

Bolt smiled. He felt touched, but didn't know quite what to say. In the end, he turned on the Jag's engine, backed out of the parking space, and once again they were on the move.

Miles Cavendish lived in the village of Stretham, about ten miles north of Cambridge on the A10, and it wasn't far short of three in the morning when Bolt and Mo finally pulled up in front of an attractive barn conversion set back a hundred yards from the road down a quiet lane.

Security lights illuminated the whole of the well-kept front garden, and as they got out of the car more lights came on in the house. By the time they got to the front door it had been opened on a chain by the man from the website photo. He was in a dressing gown and striped pyjamas and his hair was a mess. He eyed them with a mixture of suspicion and concern.

'Mr Cavendish, we spoke earlier.' Bolt placed his warrant card in the gap so that Cavendish could examine it as carefully as he wanted.

'Oh God,' said Cavendish, releasing the chain and opening the door. 'So it wasn't a hoax.'

'I'm afraid not,' answered Bolt as he and Mo stepped inside.

They followed Cavendish through to a traditionally decorated lounge and he invited them to sit down. 'I'm sorry about earlier but I've been the victim of identity fraud before and I'm very careful what I say on the phone to people I don't know. Could you please tell me what this is about?' He looked at them anxiously.

They'd decided on the way up to treat Cavendish as if he was a suspect. Which meant not giving much away.

'We can't tell you very much, I'm afraid,' Bolt replied. 'Right now, we just want you to answer our questions.'

Cavendish went white. 'We're a very respectable company, officers. We've got nothing to hide, I promise. We pay our taxes on time-'

'Firstly,' said Mo, 'can you tell me what your organization does?'

'We're a gas wholesaler. Basically, we buy certain specialist gases, directly from the manufacturers in this country and Europe, and sell them on in smaller quantities to our clients, who are mainly in the pharmaceutical and technology sectors.'

'And are there any gases your company handles that could be classed as highly expensive?'

'Yes. Some of the loads are worth a lot of money. A mixed batch of, say, xenon, tungsten hexaflouride, helium-3 isotope, could be worth as much as a hundred thousand pounds.'

That seemed to Bolt to be a lot of money for gas, but it wasn't the kind of figure worth killing people for. 'And do you handle dangerous gases as well?'

'Numerous. We deal in toxics and flammables. You'll have to be more specific.'

'What about radioactive materials?'

'No, we don't deal with radioactives. That's a very specialized area. Please, Mr Bolt, can you tell me what you're getting at?'

Bolt couldn't help feeling sorry for the guy. Unless he was an extremely good actor, it was clear he wasn't involved in Jenny Brakspear's abduction. But it was still essential that he take their enquiries absolutely seriously.

'Could you tell me if any orders for dangerous gases have been made in the past three days? Is that possible to check?'

Cavendish looked at them both in turn. 'All orders of hazardous gases or chemicals need a director's signature,' he said eventually. 'And there are only two directors. Myself-'

'And Roy Brakspear,' said Mo, finishing the sentence off for him. 'When was the last time you spoke to him?'

'Monday morning,' he answered. 'Roy wasn't feeling well. He said he'd been getting stomach cramps over the weekend. We discussed a client proposal we've got coming up but we didn't talk for long.'

'Has he been into work at all this week?'

Cavendish shook his head. 'No, we agreed it was better for him to work at home until he felt better.'

'So you haven't seen Roy at all this week?'

Again he shook his head. 'No. I tried to call him earlier on tonight to check that he was OK but he didn't answer. I assume he was sleeping. He's like me. He lives on his own.'

'But he has a daughter,' said Bolt.

'That's right. Jenny.'

'So he was married once?'

'He was. Celia passed away five years ago. She had stomach cancer. It was very tragic.'

Bolt felt a twinge of sympathy for Brakspear. He'd lost Mikaela seven years ago, yet still thought about her every day. A loss like that never really goes away, and for Brakspear to now face losing his only daughter must be unbearable. He would do anything to keep her alive. The question was, what had he done?

'Can you tell me if Roy's placed any orders for gases or chemicals this week?' he asked. 'Particularly anything out of the ordinary.'

Cavendish frowned. 'Mr Bolt, I've worked with Roy Brakspear for over twenty years now and I can assure you that he's as straight as a die. I can promise you he's done absolutely nothing wrong.'

Bolt leaned forward in his seat and fixed Cavendish with a hard stare. 'Can you just check for us, Mr Cavendish? Please.'

'OK,' he said reluctantly, getting to his feet. 'If he has, it'll be recorded on our system. I can access it from the study.'

They followed him through the lounge to a wide airy room at the back of the house where a mahogany desk faced out into the back garden, and waited in silence while Cavendish booted up his PC. When it was up and running he sat down and began typing.

Bolt rubbed his eyes and thought about Tina, wondered where she was and whether she was even still alive. He hadn't wanted to admit it to himself but, though the kidnappers might have a good reason to keep Jenny alive if they wanted her father to do something for them, they had no obvious reason to do the same with Tina. In fact, quite the reverse. She'd been investigating them, so clearly it would be better if she was out of the way. The only thing giving Bolt hope was the fact that her body hadn't been found yet, even though her car had. It wasn't much, but until he heard otherwise he'd keep searching for her.

'Nothing yet,' said Cavendish, without looking round, still tapping away on the keyboard. 'As I've said to you already, Roy's as straight as a die. He won't have made any significant orders – anything out of the ordinary, as you put it – without telling me.'

Bolt leaned against the wall, feeling frustrated. Roy Brakspear was being blackmailed, he was absolutely sure of it. No other explanation made sense. But if it wasn't something to do with his work, then what the hell was it?

'Christ.' Cavendish had stopped tapping on the keyboard and was now staring at something on the screen.

'What is it?'

Bolt and Mo hurried over to where he was sitting. On the screen was an invoice that appeared to be in German.

'I don't understand it,' said Cavendish distantly. 'Roy has put in an order. For a whole lorry load of phosgene. Now why on earth would he do that? We only ever buy it one pallet at a time.'