Caffery put his head on one side, raised his eyebrows.

'Yes. And if it was wildlife chewed it off — fish, the harbour rats, maybe — there'd be bites all over it. There aren't any. The only injury is…' she held up her hand and circled a thumb and finger round her wrist '… is here. Right here where it came away from the arm. The CSM's with me on all of this.'

Caffery stood in front of her, looking at her hair and her thin arms in the thermals. She hated it. She never quite felt her skin was on properly when she was surface-side, where other people did sophisticated things with their relationships — and that was why she'd always be better under the water. Mum, she thought, Mum, you'd know how to do this. You'd know to look normal, not surly like me.

'Well?' he said, studying her thoughtfully. 'What could have made an injury like that?'

'Could have been a boating accident, maybe. But those happen further out — in the estuary. Then there's people coming off Clifton Bridge. Suicide Bridge, we call it. If someone takes a dive round here, nine times out of ten it's off there. They can get dragged up and down the river and sometimes, sometimes, if the tide's right, they'll get washed quite a long way upstream.' She shrugged. 'I suppose theoretically if they'd come off the bridge, got cut by a boat out in the river, a stray hand might've just got past the stop gates, ended up in the harbour. Or come up through the Cut.' She pushed her hair behind her ears. 'But no. That's impossible.'

'Impossible,' said Dundas. 'It's about a million to one. And even if it came from the Frome River or higher up the Avon, down through Netham lock and into the feeder canal…'