She took a tissue from her bag and touched it to the end of her nose. “I don’t know anything about the water system. All I know is that Mummy said the pipes were always banging.”

I was relying very heavily on the fact that she knew nothing about the water system. Or any other system. My “oddities” were courtesy of Jess. “Try Madeleine with the electricity as well,” she had said. “The night I found Lily, the house was in darkness and I couldn’t get the outside lights to work. That’s the main reason I took her back to the farm. I didn’t want to waste time trying to find out which of her fuses had blown. Everything was working fine the next day, and I rather forgot about it.”

“Something else that was unusual,” I went on, “was that several of the fuse cartridges had been removed from the electricity box. If Jess hadn’t been here, I’d have spent my first night in darkness because none of the lights in the bedrooms worked. It was only when she checked the box that we discovered why. They were laid in a row on the top of the case…and as soon as they were plugged back in the lights came on.”

Madeleine played with her tissue.

“Do you know who might have done that? The police are wondering if an electrician did some work. If so, how did he get in? They’re very keen to find anyone who’s had access to the house in the last six to nine months. They’re wondering if your mother let him in…but why would he leave her in darkness?”

She shook her head.

“The really strange thing,” I said, reaching into the sink to turn on the tap and drown my fag end, “is that the valve on the oil tank was turned off but the gauge was reading full. And that doesn’t make any sense, because Burton’s last delivery was at the end of November…and your mother didn’t go into a nursing-home until the third week in January. It meant she had no hot water or cooking facilities for the last two months she was here.” I paused. “But how could that have happened without you knowing? Did you not visit her during that time?”

Madeleine found her voice at last. “I couldn’t,” she said rather curtly as if it was a criticism she’d faced before. “My son was ill and I was helping Nathaniel prepare for an exhibition. In any case, Peter came in regularly so I would have expected to hear from him if anything was wrong.”

“But not from Jess,” I said matter-of-factly. “She’d already written to tell you that she’d withdrawn her support from Lily.”

“I don’t recall that.”

“I’m sure you do,” I said, taking a copy of Jess’s letter from my pocket. “Do you want to remind yourself of what she said. No? Then I’ll do the honours.” I isolated a passage. “ ‘Whatever’s gone before, your mother needs your help now, Madeleine. Please do not go on ignoring her. For a number of reasons, I can no longer visit, but it’s in your interests to come down and organize some care for her. Without support, she cannot stay at Barton House alone. She’s more confused than Peter realizes but if you allow him or anyone else to decide on her competence you might regret it.’ ” I looked up. “All of which was true, wasn’t it?”

She abandoned denial in favour of protest. “And why should I believe it when Mummy’s GP was saying the opposite? If you knew Jess better, you’d know that stirring up trouble is her favourite pastime…particularly between me and my mother. I wasn’t going to take her word against Peter’s.”

I showed surprise. “But you and Nathaniel drove down as soon as you received this letter…so you must have given it some credence.”

There was a brief hesitation. “That’s not true.”

I went on as if she hadn’t spoken: “You sent Nathaniel to find out from Jess what ‘regret’ meant while you stayed here and tried to prise it out of your mother. Did she tell you? Or did you have to wait for Nathaniel to come back with the bad news about the power of attorney?”

I watched her mouth thin to a narrow line. “I’ve no idea what you’re talking about. The first I heard about the solicitor being in charge was when Mummy was taken into care.”

“That’s good,” I said encouragingly, “because when I told Inspector Bagley about the utilities being turned off, he said it sounded as if Lily had been subjected to a terror campaign. He’s wondering if it had something to do with MacKenzie.” I paused. “I told him it couldn’t have done-MacKenzie was in Iraq between November and January-but, as Bagley said, if not MacKenzie, who? What kind of person deprives a confused old lady of water, light, heat and food?”

Perhaps I should have predicted her answer-Jess certainly did-but I honestly hadn’t realized how slow-witted Madeleine was. The old adage about tangled webs might have been written for her. She was so caught up in the knowledge of what she and Nathaniel had done that the obvious answer-“There was nothing wrong with this house when I prepared it for let”-escaped her.

The intelligent response would have been surprised disbelief-“a terror campaign?”-and a finger pointed straight at Lily and her Alzheimer’s: “It must have been Mummy who did it. You know what old people are like. They’re always worrying about the cost of living.” Instead, she offered me her pre-prepared “culprit.” In some ways it was laughable. I could almost hear her brain whirring as she produced the “line” that she and Nathaniel had rehearsed.

“There’s only one person in Winterbourne Barton who’s that disturbed,” she said, looking me straight in the eye. “I tried to warn you but you wouldn’t listen.”

Her eagerness to implicate Jess was faintly disgusting. She looked pleased, as if I’d finally asked a question that she knew the answer to. “Jess?” I suggested.

“Of course. She was obsessed with my mother. She was always creating problems so that Mummy would have to call her up. Her favourite trick was to put the Aga out because she was the only one who knew how to relight it.” She leaned forward. “It’s not her fault-a psychiatrist friend says she probably has Munchausen Syndrome by Proxy-but it never occurred to me she’d go as far as turning off the water and the electricity.”

I smiled doubtfully. “So why didn’t she follow through?”

“On what?”

“Milking the benefits. Munchausen by proxy is an attention-seeking syndrome. It needs an audience. Sufferers make other people ill so that they can present themselves in a caring light.”

“That’s exactly what she did. She wanted Mummy to be grateful to her.”

I shook my head. “It’s not the victim who’s the audience-victims tend to be babies and toddlers who can’t speak for themselves-it’s the sympathy and admiration of neighbours and doctors that sufferers want.”

Annoyance hardened her eyes. “I’m not an expert. I’m merely repeating what a psychiatrist told me.”

“Who’s never met Jess, and doesn’t know that she’s so reluctant to attract attention to herself that hardly anyone in Winterbourne Barton knows her.”

“You don’t know her either,” she snapped. “It was Mummy’s attention she wanted-her undivided attention-and she lost interest as soon as the Alzheimer’s took over. She was happy being the constant companion but she wasn’t going to play nursemaid. That’s what that letter was about-” she jerked her chin towards the piece of paper-“shuffling off the responsibility as soon as it became arduous.”

“What’s wrong with that? She wasn’t even related to Lily.”

There was the shortest of hesitations. “Then she had no business to insist on Mummy being sectioned. Why was it done in such a hurry? What was Jess trying to hide?”

“Peter told me it was social services who ordered it, and they did it for her own safety. It was a temporary measure while they tried to locate you and her solicitor. Jess wasn’t involved…except to give them your phone number and the name of the solicitor.”

“That’s Jess’s story. It doesn’t mean it’s true. You should ask yourself why Mummy had to be silenced so abruptly…and why Jess was so keen to accuse everyone else of neglecting her. If that’s not attention-seeking, I don’t what is.”