She’d just reached the Navigation Lock, however, where the gaunt shell of a pub stood on the other side of the water, its windows boarded, when she suddenly sensed that there was someone else on the towpath. She glanced behind her and was just able to distinguish a diminutive shape some fifty yards away. Disconcerted, she glanced back again, this time for longer, trying to get a proper view of whoever it was.

The shape passed through a patch of streetlighting, and Lorna glimpsed a slim, girlish figure in a pale-grey tracksuit, wearing what looked like white trainers, with a mop of light blonde hair.

She ran on, uncertain why she still wasn’t happy. Almost unconsciously, she increased her speed a little, legs now pumping, lungs working furiously, until she was moving at what felt like a half-sprint. That wasn’t really a good idea. She still had about three miles to go, and if she kept this up she’d be exhausted long before she reached that target. She decelerated again, glancing over her shoulder a third time.

Inevitably, the figure had fallen behind a few yards and was in dimness again, so it was difficult to identify anything about her aside from her sex. That alone should have made her presence less threatening, but Lorna still couldn’t help thinking it odd that the other runner had come upon her seemingly from nowhere. Of course, that made it sound more sinister than it possibly was. The girl or woman might have been jogging along the canalside anyway, Lorna coming down the cut-through from Leatherton Lane just ahead of her. There was no reason why it couldn’t be as innocent as that. But again, at the risk of thinking like Alex, it was late, the towpath was dark and that other runner was a lone female.

Lorna had assumed that only she was bold enough to take a route like this so late at night.

She glanced behind one final time. The other runner had fallen a significant distance behind. It wouldn’t be long before she was out of sight altogether.

Now, several hundred yards past the pub, the wall on Lorna’s left gave way to rusted wrought-iron fencing and, on the other side of that, flat open ground. She knew from having run this way earlier in the year, when the evenings were lighter, that it was mostly allotments over that way; the terraced houses to which they belonged were still visible about three hundred yards distant, but only in outline. A little past the allotments, the fencing ended and the garages began. There were six of them, a terraced row, all backing onto the towpath, all disused. They were decades old and built from cheap wood: flimsy, teetering structures, their sagging tarpaper roofs ready to fall in.