Death Has a Small Voice — Frances Lockridge; Richard Lockridge

Before he dies, a murdered burglar puts Mrs. North in mortal danger

The thief struts toward Broadway, confident his luck has finally begun to turn. Just a few hours earlier, he had been as scared as a trapped rat, cowering in a bathroom, hoping the homeowners would go to bed without finding him. He got lucky, and he got away with his mark: a flimsy little piece of plastic that's worth more money than he's ever had at one time. But before he reaches his destination, he'll be left for dead on the sidewalk. As his last act, he drops his loot in the mail.
 
The package is marked for Pamela North, the slightly daffy amateur sleuth who always nabs the killer, even if she never quite gets to the point. One man has already died for this mysterious item, and as soon as it lands in her mailbox, she'll be in danger of joining him.
 
Death Has a Small Voice is the 18th book in the Mr. and Mrs. North Mysteries, but you may enjoy reading the series in any order.