‘You’re free to go.’ Palmer, leaning against the desk, signalled to the door with a wave of his hand. ‘Thanks for your time.’ He waited for Shane to open the door and then followed him casually, making sure he didn’t get lost on his way out.

When he returned to the incident room upstairs, Barrett, who had been busily talking on the phone, welcomed him.

‘Shane Matlock has been in and given a DNA sample. I wouldn’t be that surprised if it turns out he was still sleeping with his estranged wife; but I don’t fancy him for the killings.’ Palmer picked up a packet of biscuits that was lying on his desk and took one before offering them to Barrett, who politely declined.

‘I’ve had Mrs Wade on the phone. She’s keen to see Andrew. I’ve advised her against it. Visiting a prison is the last thing she needs. Poor woman needs closure, not further heartache.’

Barrett watched as a crumb tumbled down Palmer’s chin before landing on his tie. Barrett fought a strong urge to brush it off. He hated people having a scruffy appearance. He was always well turned-out. His shirt was always ironed, his shoes shined and his silver hair kept neat. Despite the fact he was a widower he had never let it jeopardise his appearance, even if he was reminded of his beloved wife every time he got the iron and board out of the kitchen cupboard. Her death had left a gaping hole in his heart and Barrett knew he would remain a single man forever more. Besides, since he’d lived alone for the last five years, he had become accustomed to doing things his way and he was sure no woman would ever put up with his deeply embedded strange personal habits.

Since the death of his wife, Josephine, the home they had shared together remained untouched. Her clothes still hung in the wardrobe, her perfume sat on her dressing table, and the house was still her home as much as it was his. Barrett had no desire to remove her memory from his life. Having her possessions around still kept him feeling close to her, as if she might return after an unusually long holiday.

On the few occasions Palmer had seen an opportunity to go into Barrett’s house, his colleague had always made excuses: the place was a mess; he was in the middle of decorating. There was always a reason why Palmer could not go inside and, as a result, Palmer found himself wondering if his boss did, in fact, live in squalor. It didn’t seem likely, given the fastidious nature of the man, but it was the only explanation he could come up with. Either that or Barrett was suffering so badly from OCD that he was paranoid about introducing other people’s germs into his house.