The end of the Bat-Signal means good times for the underworld! 
Detective Comics #121 is an issue of the series Detective Comics (Volume 1) with a cover date of March, 1947.
Synopsis for Batman: "Commissioner Gordon Walks a Beat"
Batman and Robin are summoned to the GCPD Headquarters, where they learn that Commissioner Gordon has been replaced, by orders of the mayor. Gordon has been demoted to a beat cop and Batman's deputy status is also revoked without explanation. As a result, the Bat-Signal is destroyed by the new Police Commissioner. When Batman questions the mayor he learns that underworld boss Sure Thing Smiley is extorting the mayor's son.
Batman tries to apprehend Smiley and his gang, but Smiley captures Batman instead. Batman uses Smiley's passion for gambling by betting that he can shoot Commissioner Gordon in exchange for Smiley's blackmail documents on the mayor's son. Smiley agrees to the bet with set conditions. Batman outwits him by using a bulletproof shield to protect Gordon.
By winning the bet, Batman frees the mayor from Smiley's grip. Gordon is restored as Commissioner, Batman is back with the police, the Bat-Signal is restored and Smiley is arrested.
Appearing in Batman: "Commissioner Gordon Walks a Beat"
Featured Characters:
Supporting Characters:
- Gotham City Police Department
- Commissioner Gordon
- Inspector Vane (Single appearance)
Antagonists:
- "Sure Thing" Smiley (Single appearance)
- Gomer (Single appearance)
- Torchy (Single appearance)
- Joe (Single appearance)
Other Characters:
- Chadwick Carfax (Single appearance)
- Mayor Carfax (Single appearance)
Locations:
Items:
Synopsis for Slam Bradley: "The Case Without a Key!"
Slam investigates a series of burglaries and finds graphite in the lock of one of the buildings. When he returns to his office, he realizes that he has lost his key. Slam visits a locksmith and sees graphite on the shelf. Slam then sets a trap, luring the crooks to the apartment of a wealthy tycoon. Slam and Shorty are waiting for the crooks, who were blackmailing the locksmith into making duplicate keys for them. The locksmith redeems himself by grabbing a tommy gun and helping Slam defeat the crooks.
Appearing in Slam Bradley: "The Case Without a Key!"
Featured Characters:
Supporting Characters:
- Shorty Morgan
- Sergeant Kelly
Antagonists:
- Scar
- his gang: Louie, others
Other Characters:
- Locksmith
- Coombs, oil tycoon (Mentioned only)
- Midget Circus Performers: Flip Morrison, Rocko, Swingo, Micro, others
Locations:
- New York City
- Bradley & Morgan Detectives office, 218 Grade St., 1st floor
- Locksmith shop
Synopsis for Air Wave: "Happy Jail-Day to You!"
Larry Jordan suspects that gangster Dink Dillman is hiding out on Seminole Avenue. He recruits a brave young Air-Wave fan, Tommy Murray, to become a singing messenger for the telegram company. Tommy goes door-to-door along Seminole Avenue, having one awkward conversation after another, until he finds the crooks for Air Wave. The crooks are able to knock Air-Wave out and escape, but Tommy follows them and signals their location to Air Wave. Air Wave regroups, follows Tommy's signal, then captures Dillman and his gang. At the telegram company, Tommy get promoted into an office job.
Appearing in Air Wave: "Happy Jail-Day to You!"
Featured Characters:
Supporting Characters:
Antagonists:
- Zimmy, bully
- Dink Dillman
- his gang, 2 hoods
Other Characters:
- Tommy Murray (Single appearance)
- Tommy's Mother (Single appearance)
Locations:
- New York City
- District Attorney's Office
- Seminole Avenue
- Telegraph Company
- Windmill Restaurant
Vehicles:
- Getaway Car
Synopsis for Three-Ring Binks: "Gus Crystal"
Three-Ring Binks tells one aspiring show-business glass-eater the story of an earlier glass-eater's career.
Appearing in Three-Ring Binks: "Gus Crystal"
Featured Characters:
- Three-Ring Binks
Other Characters:
- Glenn Glazer, Glass-Eating Gourmet
- Gus Crystal, Glass Eater, Inc.
Locations:
- Binks's Office
Synopsis for Boy Commandos: "The Phantom Express!"
Rip and the boys are asked to look into a mysterious "Ghost Train" that is causing many wrecks and loss of life. They eventually discover that a group of train robbers are using an airplane and some gadgets to simulate a ghost train that forces other trains to slam on the brakes, often causing derailings. The crooks are trying to get the railroad to believe in the ghost train in order to have them reroute the tracks so they can purchase the land which they have discovered is rich in pitchblende. Rip packs an anti-aircraft gun into a train car and manages to shoot down the crooks' plane and expose their plot.
Appearing in Boy Commandos: "The Phantom Express!"
Featured Characters:
Supporting Characters:
Antagonists:
- Train Robber Gang
- "Phantom Express" pilot (Dies)
Other Characters:
- Railroad Inspector Walkin (Single appearance)
- Train Engineers (Charlie named)
- Mike Farragut (Single appearance; dies) (Flashback only)
Locations:
- Along the Main Line
Items:
Vehicles:
- The Phantom Express
- series of freight trains on the "Graveyard Run"
Notes
- Published monthly by National Comics Publications, Inc.
- Air-Wave gets head-konked unconscious, with a pistol butt.
- Batman:
- Robin gets head-konked unconscious, with a vase, which breaks. Batman is knocked out by a bullet "creasing" his scalp.
- This is the first time that the Bat-Signal is destroyed in Batman's history.
- "Commissioner Gordon Walks a Beat" is reprinted in Batman Archives Vol 6.
Trivia
- In Boy Commandos, Rip Carter tells the railroad manager that he "ran a 40 and 8 all the way across France," which showed him that Rip knew how to operate a steam locomotive. And maybe he did, and could, but a 40 and 8 was a type of boxcar, used in France during World War I.
- One of the newspapers in the Slam Bradley story is The Daily Bugle.
- Also appearing in this issue of Detective Comics were:
- Editorial Advisory Board (promotional text)
- "Q Is for Quagga" (2/3 page ad for the current issue of Funny Stuff #19)
- "The Pink Sheet" (text story) by Dalton Warren
- Morton by Phil Berube
- "Two of America's Most Famous Boys!" (full page ad for the current issues of Star-Spangled Comics #66 and Adventure Comics #114)
See Also