I could picture Mrs. Decarno watching Claudia through the peep-hole in her door, as she had done to me when I lived there. She was an evil-minded old woman who spiked every sentence with insults and insinuations. Still, it was hard not to smile at her dubbing Claudia a minx.

“After that, there was no noise from your sister’s apartment,” said Renfrew. “It might have been empty for two, maybe even three weeks.”

“People are fuzzy on dates,” said Bruxton. “Wendy Malahoff in 5D went off to Malaysia on a business trip, and she seems to be away most of the time. Mrs. Felesky in 5C hurt her leg in mid-September and moved to Ohio to be with her kids. Of course, your sister didn’t tell people she was going away.”

“Then, sometime in the fall, this other girl appeared,” Renfrew continued. “She was quiet. No one really noticed her, except your superintendent.”

“Mr. Pete is amazing,” said Jesse. “He has a photographic memory. He can recite every line from every movie he’s ever seen.”

“He’s sharp as a tack,” said Renfrew. “He noticed that this girl wore a whopper of an engagement ring. We found a Tiffany box with the diamond in the back of her lingerie drawer. Only, guess what, it’s the wrong ring.”

“What?”

“The one at the apartment is a two-carat princess cut in a Tiffany setting. We showed it to Mr. Pete, and he said it was nothing compared to the one she was wearing. Smaller ring, wrong style, not an antique.”

“The two-carat diamond wasn’t big enough for her?” I asked, incredulous. Martin had wanted to buy me a golf-ball sized diamond when we got engaged, but that didn’t appeal to me. He’d finally found a two-carat ring we agreed was beautiful. I’d loved it, but it was so big I felt conspicuous wearing it out. I’d never gotten used to the weight of it on my hand. As sad as I was to give it back to Martin before I left for Spain, it was a relief not to be responsible for it anymore.

“Go figure,” said Renfrew. “Assuming Mr. Pete is right, this antique diamond ring is gone. History. It’s not in the apartment.”

“And somebody stole her laptop computer,” Bruxton added.

Now I was completely confused. “What laptop?”

“CSU says there was one on the desk in the living room. The power cable is still there, and there’s a credit-card charge to Claudia Moore for the computer. She bought it in the middle of November.”

“Are you kidding? My sister doesn’t have a credit card.”