The first thing Andrea Devern noticed when she stepped out of her Mercedes C-Class Cabriolet was that there were no lights on in the house. It was 8.45 p.m. on a breezy Tuesday night in mid-September, and she had only a minute of normality left in her life.

Clicking on the Mercedes' central locking, she walked the five yards to her front gate, glancing both ways along the quiet residential street because as a Londoner born and bred Andrea was never complacent about the potential for street crime, even in an area as upmarket as Hampstead. Criminals moved around these days. They no longer kept to their own patches. They gravitated towards the money, and on Andrea's tree-lined avenue of grand three-storey townhouses, barely spitting distance from the Heath, there was plenty of that.

But there was nothing out of place tonight, unless you counted the fact that her house was in darkness. Andrea tried to remember if Pat had told her that he had arrangements, or whether he'd taken Emma off somewhere. She'd had a stressful day dealing with the management team of one of the five health spas she and her business partner owned. They'd taken it over a year ago and it had underperformed ever since. Now they were going to have to make redundancies, something that Andrea never liked doing, and it was up to her to decide who was for the push. She'd been mulling over who was going to have to go all the way back from Bedfordshire, and still she couldn't decide. By rights, it should be the manager. He was paid well over the odds, and since he was the one who'd presided over the mess the spa was now in, it appealed to Andrea's sense of justice to give him the boot; but with no one to replace him, that was looking less and less viable. Better the devil you know, and all that.