Rhona shook her head.

‘Right. I’ll bring you back a sandwich then.’ Chrissy wasn’t asking. She was telling. It was like having your mother working for you.

Rhona watched Chrissy emerge below. A bloke on the other side of the street crossed to meet her, his shaved head bowed and his hands in his pockets. It looked as if Chrissy was giving him a right mouthful. The latest in a long line of boyfriends or one of Chrissy’s brothers on the scrounge, Rhona thought.

Bill Wilson contacted her halfway through the afternoon and asked how things were going. She told him what she’d told Dr Sissons.

‘I’m working on the hairs just now,’ she said. ‘It’ll take us a while to examine the cover thoroughly, but you can have the whisky glasses back. I’ve finished with them.’

‘Thanks, although I don’t hold out much hope of finding our suspect’s prints on file.’ Bill sounded resigned. ‘By the way, the story’s splashed all over the evening paper.’

‘Right.’

She heard a short ‘mmm’ of displeasure.

‘If anyone pesters you for info?’

‘I don’t have any. Oh, and Bill.’ She hesitated. ‘Were you right?’ she asked.

‘About what?’

‘The English connection.’

‘We haven’t found out who the boy was or where he came from. But you can read that in the Glasgow News. They always know more than us anyway.’

Rhona stopped work at five o’clock. Her eyes were tired from peering down the microscope and the lunchtime sandwich had long since been eaten. Chrissy had left at four, pleading a ‘domestic’ to sort out. One look at Chrissy’s face convinced Rhona not to ask any questions.

Now, all she wanted was something substantial to eat and a long hot soak in the bath. But that meant facing Sean. She started to tidy the lab, methodically filing away her notes and storing the samples, putting off the moment when she would have to go home.

Outside, the rain had moved off north towards the Campsie Hills. The sky had cleared to a dull blue. She was a twenty minute walk from the flat and as long as the evening was fine there was no point in taking a bus. It would just sit in traffic anyway. She headed for Byres Road.

She knew Sean would have already bought something for tea but she stopped at the pasta shop anyway. Mr Margiotta welcomed her with his usual patter and persuaded her to try the spinach and ricotta cannelloni, adding an extra dollop of tomato and basil sauce for good measure.

‘Love food,’ he promised with a wicked grin.

Just what she didn’t need.

Rhona allowed herself five minutes to decide what she was going to do, before she put her key in the lock. Part of her wished she could just forget what she’d seen in the Art Gallery, but it was like a forensic clue and she couldn’t let it go. Like one of those semen samples. She had to know whose it was.