Zach Robinson is private investigator who appeared in "The Late Shaft". Talk show host Bobby Mann had secretly sent a hundred thousand dollars to him, which made Beckett and Castle suspect he had been blackmailing Bobby, and possibly even murdered him. He says he has never seen the blackmail picture, but he does have a story to tell. Bobby paid him to bug Howard Weisberg's office. Robinson explains that Bobby was suspicious and wanted to know what was going on. He delivered the CDs with the recordings to Bobby on the morning before he was murdered.