I clear my throat. “My sister-in-law, Melissa. Last Sunday—not this one just gone, the one before. She . . .” I can’t finish the sentence.

“She was in your car?” Sergeant Sam helps me out. “She noticed the mirror wasn’t there?”

Shit. Shit. What do I say?

“Yes. I drove to her house to pick her up so that we could go to an auction together. She likes auctions,” I add pointlessly. And I don’t. I go to keep Melissa happy, and I never buy anything because I hate the principle: see something, love it, bid for it, possibly go home empty-handed. No, thanks. “Then, afterward, I gave her a lift home.”

“Where does Melissa live?” asks Waterhouse.

“What’s that got to do with anything, for God’s sake?” I snap.

“If we check out your story and it holds water, that counts toward credibility,” Sergeant Sam explains.

“She lives in Highgate,” I tell him rather than Waterhouse, rooting around in my handbag. I pull out a crumpled leaflet and hand it over. “There you go. Proof that an auction took place in Grantham a week last Sunday. Satisfied?”

“Grantham,” says Waterhouse, as if it’s a bad word. “That’s, what, half an hour’s drive from Spilling?”

“Yes. Why don’t you email the auction people? I’m sure they’ll happily add you to their mailing list. I picked up a fantastic grandfather clock once—it was an absolute steal.”

“Sister-in-law’s name and phone number?” Waterhouse is ready to write it down.

“Melissa Redgate.” I recite a number that is almost hers, but with the six and the four in the wrong order. That should give me time to get to Melissa before the police do. I’ll have to throw myself on her dubious mercy.

Waterhouse doesn’t bother to thank me. One of the advantages of deliberately misleading people: when they turn out to be rude and ungrateful, you’re pleased you didn’t make the mistake of treating them well. Retribution in advance.

“Where were you between eight thirty A.M. and ten thirty A.M. yesterday?” Sergeant Sam asks me.

“At home. I think I set off around about ten thirty to take Ethan’s gym bag to school. Before then I was in my kitchen, calling or being called by the school secretary, about five hundred times.”

“Why so many times?”

“First, Ethan thought he’d be OK without his bag; then he got upset; then they thought they’d found him a spare shirt; then it didn’t fit properly; then he thought he could manage; then he changed his mind . . .”

“These calls were on your landline or your mobile?” asks Waterhouse.

“Landline.”

“And what about at eight minutes past eleven A.M.? Where were you then?”