But the feeling of disquiet stayed with me. After Toby and Doug had left I went upstairs to Hannah’s bedroom and nervously opened her door. I was usually too afraid to look in there, fearful of what I might find – a glimpse inside her head was not something I normally relished. It was always a disgusting mess anyway and today was no exception: clothes were strewn everywhere, dirty plates and mugs littered every surface. In fact, everything looked exactly as it always did. I backed out and went to work myself.

But I couldn’t stop thinking about her. She’d looked so completely different. Could it possibly be that Hannah had somehow grown up, turned over a new leaf and decided to become an ordinary, functioning member of society at last? I allowed myself to indulge in that fantasy all day.

When I got home from work, however, it was to find that she was dressed again in her usual grubby attire. The nose ring and eyebrow piercing were back in place, as was the thick black eyeliner and bad attitude. The fresh-faced and presentable young woman of earlier had completely disappeared, and my daughter was as hostile and as unreachable as ever.

But from then on, once a week, the same thing would happen. Hannah would appear early for breakfast dressed in pretty, fashionable clothes, her hair neatly brushed and with subtle make-up in place. Sometimes she’d return within an hour, her face like thunder as she stormed upstairs to lock herself in her room, but usually she’d stay out all day, with a pleased, self-satisfied expression as she strolled back through the front door. After a while I gave up asking where she’d been: I could sense she enjoyed my confusion far too much ever to tell me.

A few weeks later the phone calls began. She always seemed to be expecting them, always ready and waiting by the upstairs extension, snatching up the receiver as soon as it began to ring. She’d mumble a ‘hello,’ then pull the lead into her room, shutting the door and talking in hushed whispers.

In the end I couldn’t stand it any longer: I decided to follow her. It was a warm day in September. She came down as usual all dressed up and as soon as she left the house I called into work, quickly leaving a message to say I’d had a family emergency and wouldn’t be in until later. When I emerged on the street I saw her disappearing around the corner and got into my car to follow her, keeping a safe distance behind and parking out of sight when I saw her waiting at the bus stop.