Nicola got in her car, a little girly Ford Ka, and took off like a rocket for Stansted. Jackson wasn't exactly a slow driver but Nicola went at terrifying speeds. When this was over he was considering alerting someone in traffic. Jackson had done a stint in traffic before plainclothes and there were times when he would have liked to pull Nicola over and arrest her.

His phone rang again as the traffic slowed in a holding pattern around Stansted. This time it was his secretary, Deborah, who snapped, "Where are you?" as if he was supposed to be somewhere else.

"I'm fine, thank you. How are you?"

"Someone phoned. You may as well go and see them while you're out and about." Deborah said "out and about" as if Jackson were getting drunk or picking up women.

"Do you want to enlighten me further?" he asked.

"No," Deborah said. "Something about finding something."

Once Nicola arrived at the airport her movements followed their usual routine. She parked her car and went inside the terminal, and Jackson watched her until she disappeared from view. After that he went to the toilets, had a double espresso from a paper cup that did nothing to cool down the heat of the day, purchased cigarettes, read the headlines in a newspaper that he didn't buy, and then drove away again.

By the time Nicola's plane to Prague was climbing steeply away from the flat countryside below, Jackson was walking up the path of a large house on Owlstone Road, frighteningly close to where Binky Rain lived. The door was answered by a woman stranded somewhere in her forties who squinted at Jackson over the top of a pair of half-moon spectacles. Academic, he thought to himself.

"Mrs. Land?" Jackson said.

" Miss Land," she said. "Amelia Land. Thank you for coming."

Amelia Land made a terrible cup of coffee. Jackson could already feel its corrosive effect on his stomach. She was wandering around the neglected kitchen, searching for biscuits, even though Jackson had told her twice that he didn't want one, thank you. Finally, she retrieved a packet of damp digestives from the depths of a cupboard and Jackson ate one just to keep her happy. The biscuit was like soft, stale sand in his mouth, but Amelia Land seemed satisfied that her duty as a hostess had been done.

She seemed very distracted, even mildly deranged, but, living in Cambridge, Jackson had got used to university types, although she said she lived in " Oxford, not Cambridge. It's a completely different place," and Jackson had thought, "Yeah, right," but said nothing. Amelia Land kept babbling on about blue mice, and when he'd said gently to her, "Start at the beginning, Miss Land," she'd carried on with the blue-mice theme and said that was the beginning, and "Please call me Amelia." Jackson sighed inwardly, he sensed this tale was going to take a lot of coaxing.

The sister appeared, disappeared, and then reappeared, holding in her hand what looked like an old doll. You would never have taken them for relatives, one tall and heavy, her hair graying and falling out of a kind of topknot, the other short and curvy and – Jackson knew this type too – flirting with anything male and still breathing. The sister wore bright red lipstick and was dressed in what looked like secondhand clothes, layers of mismatched eccentric garments, her wild hair piled haphazardly on her head and fixed with a pencil. They were both dressed for cold weather rather than the sweltering day outside. Jackson could see why – he had shivered as he crossed the threshold, leaving the sunshine behind for the wintry gloom of the interior.

"Our father died two days ago," Julia said, as if it were an everyday nuisance. Jackson looked at the doll on the table. It was made of some kind of grubby toweling material and had long thin legs and arms and the head of a mouse. And it was blue. Understanding finally dawned. He nodded at it. "A blue mouse," he said to Amelia.

"No, the Blue Mouse," she said, as if that distinction were vital. Amelia Land might as well have had "unloved" tattooed on her forehead. She was dressed in a way that suggested she'd stopped shopping for new clothes twenty years ago and that when she had shopped for clothes it had been exclusively in Laura Ashley. The way she was dressed reminded him of old photographs of fishwives – clumpy shoes and woolen tights and a cord dirndl skirt and around her shoulders some kind of shawl that she was hugging to herself as if she were freezing, which wasn't a surprise because this place was Baltic, Jackson thought. It was as if the house had its own climate.

"Our father died," Amelia said brusquely, "two days ago."

"Yes," Jackson said carefully. "Your sister just said that. I'm sorry for your loss," he added, rather perfunctorily because he could see that neither of them seemed particularly sorry.

Amelia frowned and said, "What I mean is…" She looked at her sister for help. That was the trouble with academic types, Jackson thought, never able to say what they mean and half the time never meaning what they say.

"Let me hazard a guess," he said helpfully. "Your father died -" They both nodded vigorously as if relieved that Jackson had grasped this point. "Your father died," he continued, "and you started clearing out the old family home -" he hesitated because they looked less sure of this, "This is the old family home?" he checked.

"Well, yes," Julia said. "It's just" – she shrugged – "that sounds so warm, you know. 'Old family home.'"

"Well," Jackson said, "how about we remove any emotional significance from those three words and just treat them as two adjectives and a noun. Old. Family. Home. True or false?"

"True," Julia admitted reluctantly.

"Of course, strictly speaking," Amelia said, staring out the kitchen window as if she were talking to someone in the garden, "'family' isn't an adjective. 'Familial' would be the adjective."

"No, it wouldn't," Julia said.

Jackson decided the best thing would be to carry on as if neither of them had spoken. "Not close to the old guy then?" he said to Julia.

"No, we weren't," Amelia said, turning round and giving him her full attention. "And we found this in a locked drawer in his study." The blue mouse again. The Blue Mouse.

"And the significance of the 'Blue Mouse'?" Jackson prompted. He hoped they hadn't just discovered their old man was some kind of soft-toy fetishist.

"Did you ever hear of Olivia Land?" Julia asked.

"Rings a bell," Jackson said. A very small bell. "A relative?"

"She was our sister," Amelia said. "She disappeared thirty-four years ago. She was taken."

Taken? Oh, not alien abduction, that would really make his day. Julia took out a packet of cigarettes and offered him one. She made offering a cigarette seem like an invitation to sex. He could feel the sister's disapproval from where he sat but whether it was of the nicotine or the sex, he wasn't sure. Both probably. He declined the cigarette, he would never have smoked in front of a client anyway, but he inhaled deeply when Julia lit up.

"She was kidnapped," Julia said, "from a tent in the garden."

"A tent?"

"It was summer," Amelia said sharply. "Children sleep outside in tents in the summer."

"So they do," Jackson said mildly. Somehow he had the feeling that Amelia Land had been the one in the tent with the sister.

"She was only three," Julia said. "She was never found."

"You really don't know the case?" Amelia said. "It was very big."

"I'm not from this area," Jackson said and thought of all the girls who must have disappeared over the last thirty-four years. But, of course, as far as the Land sisters were concerned, there was only one. He felt suddenly too sad and too old.

"It was very hot," Amelia said. "A heat wave."

"Like now?"