The Burglar in the Closet by Lawrence Block
It's hard to ignore someone with his hands in your mouth. Bernie Rhodenbarr's all ears when Dr. Sheldrake, his dentist, starts complaining about his detestable, soon-to-be-ex wife, and happens to mention the valuable diamonds she keeps lying around the apartment. Since Bernie's been known to supplement his income as a bookstore owner with the not-so-occasional bout of high-rise burglary, a couple of nights later he's in the Sheldrake apartment with larceny on his mind - and has to duck into a closet when the lady of the house makes an unexpected entrance. Unfortunately he's still there when an unseen assailant does Mrs. Sheldrake in... and then vanishes with the jewels. Bernie's got to come out of the closet some time. But when he does, he'll be facing a rap for a murder he didn't commit - and for a burglary he certainly attempted - unless he can hunt down the killer who left him hanging.