Cat and mouse

by William Campbell Gault

From fantasticfiction.com: "It starts with the dead cat. Ex-private investigator Brock Callahan finds the Siamese by his mailbox, its throat cut, and assumes it is a message from some crook he put away long ago. Soon a letter arrives - "The cat was first. Who is second?" - and Brock knows the threat is no joke. He hires his protege, the ambitious young detective Corey Raleigh, to help him guard his wife and housekeeper, but Corey has troubles of his own. The kid detective is about to get an inside look at the workings of criminal justice. The cops find Corey not far from Brock's house - half-conscious with a gun in his hand and a dead man at his feet. It's an obvious frame-up, but to clear Corey's name Brock will have to find the real killer, and lock him away before his wife meets the same fate as the unfortunate Siamese."