‘I’ll need anyone who entered the flat to make a statement and retrace their steps to avoid DNA or tissue contamination,’ she instructed. ‘Can you describe the scene from when you arrived?’

‘Sure, we were pretty certain there was no active fire, as there wasn’t any smoke coming out into the hallway, but even from the floor below, there was a coppery, sulphuric smell, which was very strong when we were at the flat door.’

‘Indicating?’ Ava asked.

‘The sulphuric smell often comes from burning human hair. It’s the chemical that keratin gives off when it burns. The coppery odour can also come from burning meat if it’s very bloody, but if it’s been in a kitchen, the smell is usually contained.

‘We knocked on the door hard and then took the decision to break it down when there was no response. We found the male lying on the lounge floor. He hasn’t been moved, as it was obvious he was dead as soon as we saw him. All my officers did was turn off the electricity and unplug the toaster, then we checked the rest of the flat for people or other fire sources. As soon as it was secure, we called you.’

Ailsa Lambert strode in, issuing a barrage of orders to clear the scene immediately. She started photographing the body within seconds, addressing Ava without looking over to her.

‘Just when I thought I’d seen everything, human beings stoop to new lows. This man’s been dead no more than an hour, rather less, I’d think.’

She got down on her knees and took a close-up shot of the cable tie that held his wrists together, then looked into the digital camera’s viewfinder screen, enlarging the shot.

‘Ava, you have a problem,’ Ailsa declared.

‘I take it by your tone that you mean a greater problem than a semi-naked man lying tied up and dead on the floor?’

‘I absolutely do. It’ll take more detailed investigations, but judging by the product mark, and the manufacturing groove in the nylon, there’s a good chance these cable ties came from the same batch used in the Fenella Hawksmith murder.’

‘Show me,’ Ava said, bending down next to her.

‘Here,’ Ailsa said, ‘on the square section the tail is threaded through, there’s a diagonal nick where the nylon is lifted away from the production line. It’s at the same angle and the same length as the other cable ties, and the product code is B80, same as before.’

‘There must be millions of them in circulation,’ Ava said.

‘Of course, but two of them have turned up attached to bodies in this city, restraining victims prior to death. How likely is that?’

Ava ran her hands through her hair.

‘No you don’t, not in my crime scene. I don’t need any more hairs on this floor. Hands down and hood up.’