No, no, no and no, you silly geese...
Fortunately, the U.S. Postal Inspection Service is on the job!!
Howz about...he's stealing checks...so figure out where they're being cashed and work from that end?
Howz about, I dunno, checking the postmark on the bleeding letter?
Howz about...it's a registered letter, right? Those are supposed to be tracked, right? Even in 1948, you must know what postal branches they go through, right??
Howz about...you check for fingerprints on the envelopes? He's not wearing gloves...
Nope, they're right. Not a single lead. But that won't stymie the U.S. Postal Inspection Service, nosirree. See, our unnamed agent has a plan!
From Real Life Comics #44 (1948)