"If you're right about him knowing her," Sam said, "and about him not meaning to kill her, then couldn't he have moved her because he cared about her? He felt guilty enough already, didn't want to leave her out in the rain ..."

"I thought about that. But this guy's smart, he thinks ahead, and he was very serious about not getting caught. Moving her meant getting blood on himself, leaving more footprints, taking more time, maybe leaving hairs or fibers on her . . . I can't see him taking that kind of extra risk just out of sentimentality. He had to have a solid reason. Checking whether she was dead wouldn't take long--less time than moving her, anyway--so my best guess is that he followed her, and moved her, because he needed to search her."

"What for?" Sam asked. "We know he wasn't after cash."

"I can only think of three reasons," I said. "One is that he was checking for anything on her that might identify him--making sure she hadn't written down the appointment in a diary, trying to delete his number off her mobile, that kind of thing."

"She didn't keep a diary," Frank said, to the ceiling. "I asked the Fantastic Four."

"And she'd left her mobile at home, on the kitchen table," Sam said. "The housemates say that was normal; she always meant to bring it on her walks, but she mostly forgot it. We're going through it: nothing dodgy so far."

"He didn't necessarily know that, though," I said. "Or he could have been looking for something more specific. Maybe she was supposed to give him something, and that's what went wrong: she changed her mind . . . Either he took it off the body, or she didn't have it on her in the first place."

"The map to the hidden treasure?" Frank inquired, helpfully. "The Crown Jewels?"

"That house is full of old bits and bobs," Sam said. "If there was something valuable in there . . . Was there an inventory done, when your man inherited?"

"Ha," Frank said. "You've seen it. How would anyone inventory that? Simon March's will lists the good stuff--mostly antique furniture, a couple of paintings--but that's all gone. The death duties were massive, anything worth more than a few quid had to go to pay them off. From what I've seen, all that's left is your basic attic tat."

"The other possibility," I said, "is that he was looking for ID. God knows there's enough confusion around this girl's identity. Say he thought he was talking to me and then had doubts, or say she dropped a hint that Lexie Madison wasn't her real name: your guy might have gone looking for ID, trying to figure out who he'd just stabbed."