Saturday, 25th of November

The house on the terrace was quiet on a Saturday afternoon, all week it had been like Glasgow Central on Fair Friday, but everybody was out today. Colin Anderson had the whole house to himself. He was lying on the sofa, nursing a large Merlot and two sore feet after helping Brenda make an early start on the Christmas shopping. He was musing at the wine, as it swirled round the contours of the glass, admiring the patterns it left in the light of the wood-burning stove. His grandchild, Baby Moses, was asleep in his basket at Anderson's feet. Nesbit, the fat Staffie, was curled up on the sofa, ears tucked in so he didn't hear the rain battering against the windows. American Beauty played on the DVD, with the volume too low to hear.

It was almost perfect yet Anderson was not at peace. He was still digesting the news that his partner for twenty years had resigned. Costello was gone. No notice. No chat. No goodbyes. She had walked into ACC Mitchum's office unannounced, uninvited and slapped her letter of resignation on the desk right in front of him.

Just like that.

Twenty years they had worked together, fought, made up and fallen out again, shared laughs, heartache and a few broken bones. She had always had his back. He had always had hers. At times, their thinking was polar, opposite points of the compass, balancing each other into a relationship that while turbulent, was effective. Their track record proved that. Now she was gone. Brenda, his wife, had explained it simply. The events of the last few months had been too intense. Costello had found Archie Walker. Anderson had found Baby Moses.

Both of them had moved on and maybe George Haggerty had been the catalyst that finally separated them.

But then Brenda would say that. She had never really liked Costello.

He checked his phone. He was meeting the guys tomorrow for fish and chips, a long-standing arrangement. Costello had been invited. She had declined.

Anderson could accept that she had resigned in a fit of pique, saying she could do more about Haggerty without the restriction of the badge. She thought 'killing the bastard' would do her more good than any counselling.

And she had been furious when her request to form a task force to investigate the murders of Abigail and Malcolm Haggerty had been refused. The case had been transferred to Complaints and Internal Investigations, purely for clarity and transparency, but to him, and Costello, it felt they themselves were being scrutinized and judged. The first two people on the murder scene were members of the law enforcement community, and not just any members; a DI and Chief Procurator Fiscal. And as the fiscal's goddaughter was the victim's sister, the press were having a field day.

Haggerty was now talking to the media, playing on the 'Monkey House of Horror' crap. The case had rarely been out the papers for the last six weeks. Every day there was another tasty morsel revealed by the press. One thing they were all agreed on: the police weren't coming out of it well. George Haggerty was the obvious suspect and he was the one man who couldn't have done it. Even ACC Mitchum let slip that he too, had taken a very close look at that alibi. He had personally interviewed the two police officers who had caught Haggerty speeding in his white Volvo on the A9. One obvious suspect. Police Scotland were his alibi.

Yet, Costello had persisted that George Haggerty had killed his family.

He looked down at the bundle of pink skin in the Moses basket. His grandson, his link with Haggerty, the one reason they kept in touch. Anderson didn't like Haggerty, not the way his daughter Claire did. God, she had even drawn him a portrait of Baby Moses in pastel and had left it for him, signed and wrapped. Anderson wished she hadn't bothered. There was nothing he could define, nothing he could specify, just a very intense feeling of dislike. If he himself had one tiny piece of physical evidence against Haggerty, Anderson would have brought him in and every bone in his body would have told him that he had the right bloke. Every time, he was in Haggerty's company, Anderson could sense smirking guilt.

Anderson watched the Merlot, tipping it to the left and right. 'He has a watertight alibi,' he said out loud, 'and no motive at all.' He looked at his grandson, blowing bubbles in his basket. 'Well, none that we have found.' Moses ignored him but Nesbit cocked an ear. 'George Haggerty did not kill his wife Abigail or his son Malcolm. He couldn't have done it.'

To his mind the best way of getting Costello back was to prove her wrong and get DCI Mathieson and her team to prove that somebody else did kill Abigail and Malcolm. Then maybe Costello could get closure and move on. And then she might come back into the fold as it were. He could see how the lack of progress in the case might have frustrated his colleague. The killer had ghosted in and out the house, without leaving a trace. Or a trace was there because it had a right to be there. The Haggertys were not a social couple so the only 'other' DNA in the house was Abigail's sister, Valerie Abernethy, and she had stayed overnight only a few days before the killings. No fingerprints, no footprints but the blood spatter had left a clean zone where the killer had stood and that indicated they were slim, five feet ten or more. George was five seven.

It had also really annoyed Costello to learn that Dali Despande's proposal to pilot a new fast-track child protection service had been side-lined, again. Looking back, Anderson thought, maybe she hadn't been right since the Kissel case, that child being starved to death, neglected by a mother who didn't care, let down by a failing social work system. It had taken that little boy weeks to die. Costello had sat in the court and relived every minute of the harrowing abuse. Then Malcolm? Costello had in her head that Malcolm was a vulnerable child.

Then she had walked into that scene, a scene so awful, it was reported that the crime scene photographer on duty had been off work since with stress, unable to cope with what he had seen.

Still none of it was any of his business. He had to walk away and leave it to Mathieson and Bannon. He had his cold case rapes to work on. Mitchum had given him one more week before the file went back to the freezer.

ACC Mitchum had been very clear; Anderson's loyalty was to the force.

Not that there was any conflict of loyalty, Costello had not been in contact for twenty-one days.

The Monkey House Of Horror.

The tabloids hadn't been able to resist that.

Valerie Abernethy looked up at the familiar ivy-covered eaves, the two red chimneys, the big, stained-glass window all hidden from the road by the majestic monkey puzzle tree. Had it been a happy family home for her sister? The gutter press thought so. A happy family home that became a scene of slaughter.

Valerie took a deep breath, trying to calm the panic. They wanted her to walk round the room where her sister had breathed her last, shielding her son from the blade of a knife. She was aware of the investigative team hovering at the bottom of the gravel drive, pretending they were giving her a little moment to catch her private thoughts. She knew she was under scrutiny.

Well, they could stand there, out in the rain, a little longer. Valerie placed her hand on a petal of the stained-glass flower, a delicate stem with Mackintosh roses. The glass felt slightly...