‘Drug overdose.’ she said quietly. ‘After Emily Drennan died I was really screwed up, and in the end it wrecked my marriage. Robert went to live abroad, and refused to take Hannah. She was gutted by his rejection, and blamed me for everything.’

‘And went off the rails?’

Nikki gave a short, barking laugh. ‘Oh no! Not Hannah! She was far too clever to do that! She had a master plan. Her one aim in life was to make me suffer. Every day, in every way.’

‘So she dabbled with drugs, just to piss you off?’

Again Nikki shook her head. ‘No, but she did start mixing with some seriously dubious characters, just for my benefit. Then she made the mistake of confiding in someone who hated me even more than she did, someone who was much cleverer than Hannah, and totally unscrupulous.’

‘Don’t tell me,’ breathed Joseph. ‘Frankie Doyle.’

‘Got it in one, Sergeant.’ Nikki pulled into the Carborough and made her way confidently through the maze of streets. ‘And it was Archie Leonard who helped me find out what had happened, and gave me the name of Frankie Doyle.’

‘What did happen?’ asked Joseph.

‘I believe Doyle got hold of a bad batch of drugs.’ Nikki faltered for a second, then she took a deep breath and said. ‘And she spiked Hannah’s drink with enough junk to fell an ox.’

‘She meant to kill her?’ Joseph’s voice rose an octave.

‘I’m sure she did. What better way to get at me, but I could never prove it. Even the info that Archie managed to get hold of was obtained through a dozen back doors. Only one man could ever help me, and that was the dealer who sold Frankie the junk, so you can see where that led me, can’t you?’

‘You’ve been on a one-woman witch-hunt ever since.’ Joseph exhaled loudly. ‘But why did Archie help you? You may have had some weird good guy–bad guy relationship, but you’re still the Old Bill.’

Nikki pulled into a space, switched off the engine, then looked up and almost gasped. ‘Another time, Sergeant. Take a look at that!’

In front of them was the end wall to one of the smaller blocks of flats, and painted across it in giant multicoloured letters, were the words, MASK WARS.

‘Shit!’ Joseph jumped out of the car and ran over to the uncommissioned art work. ‘Graffiti artists sign their work with a tag.’ He searched the bold swirls and slashes of vivid colour. ‘Yeah! Got it. Look.’

Nikki caught up with him and peered at the strange hieroglyphic. ‘What’s that? Looks like P-I-E-T to me. Ring it in, Sergeant, get Cat or Dave to run a check for us.’