Queen’s Bureau of Investigation is now open for business – and in each department of this new enterprise Ellery finds ample opportunity to exercise the brilliant, ingenious, and at times startling talents of his crime-laboratory mind. For to the bureau come some of the most plaguy cases in Queen’s career, including: 
“The Three Widows” – of whom two were wealthy Theodore Hood’s daughters and one his widow, all caught in a murder that Ellery reluctantly relegated to the Impossible Crime Department.
 “The Myna Birds” – the story of old Mrs. Andrus, whose bequest of a million dollars to thirty-eight observant and talkative birds sets off a chain of violent events leading straight to the Embezzlement Department – and the only bird-detective on record!
 “A Question of Honor” – a matter of considerable international delicacy, involving indiscreet letters, a Shakespearean scholar from Scotland Yard, and a crime at once assigned to the Suicide Department.
And numerous other criminals, crimes, follies and felonies find their way to the bailiwicks of the Q.B.I. From the files of the Buried Treasure Department comes “Miser’s Gold”; from the Narcotics Department, “The Black Ledger”; from the Kidnapping Department, “Child Missing!”; - and many others. In each and every case, Ellery Queen demonstrates the powers that make him unique among detectives.”

• BLACKMAIL DEPT. -- "Money Talks" (This Week, 4/2/50 as "The Sound of Blackmail" reprinted in EQMM 08/52)
• FIX DEPT. -- "A Matter of Seconds" (This Week, 8/9/53 reprinted in EQMM 01/57)
• IMPOSSIBLE CRIME DEPT. -- "The Three Widows" (This Week, 1/29/50 as "Murder Without Clues"; reprinted in EQMM, 2/53,)
• RARE BOOK DEPT. -- "My Queer Dean!" (This Week, 3/8/53, reprinted in EQMM, 11/56)
• MURDER DEPT. -- "Driver's Seat" (This Week, 3/25/51 as "Lady, You're Dead") 
• PARK PATROL DEPT. -- "A Lump of Sugar" (This Week, 7/9/50 as "The Mystery of the 3 Dawn Riders" reprinted in EQMM, 2/53 and in EQMM, 03/69 as "Murder in the Park")
• OPEN FILE DEPT. -- "Cold Money" (This Week, 30/03/52 and EQMM, 01/56)
• EMBEZZLEMENT DEPT. -- "The Myna Birds" (as "The Myna Bird Mystery" in This Week, 12/28/52 reprinted in EQMM, 9/56 as "Cut, Cut, Cut!" )
• SUICIDE DEPT. -- "A Question of Honor" (This Week, 9/13/53 reprinted in EQMM 05/58)
• HOLDUP DEPT. -- "The Robber of Wrightsville" (in Today's Family, 2/53 as "The Accused" and in EQMM, 12/54)
• SWINDLE DEPT. -- "Double Your Money" (This Week, 9/29/51 as "The Vanishing Wizard" reprinted in EQMM, 9/55)
• BURIED TREASURE DEPT. -- "Miser's Gold" (This Week, 6/18/50 as "Love Hunts a Hidden Treasure"; The Sunday Herald 07/16/50 as "Love Hunts a Hidden Treasure"; reprinted in EQMM, 4/54; as "Death of a Pawnbroker" EQMM 11/71)
• MAGIC DEPT. -- "Snowball in July" (This Week, 8/31/52 as "The Phantom Train" reprinted in EQMM 07/56)
• FALSE CLAIMANT DEPT. -- "The Witch of Times Square" (This Week, 11/5/50 reprinted in EQMM, 5/53)
• RACKET DEPT. -- "The Gamblers' Club" (This Week, 1/7/51 reprinted in EQMM, 3/55)
• DYING MESSAGE DEPT. -- "GI Story" (EQMM, 8/54)
• NARCOTICS DEPT. -- "The Black Ledger" (This Week, 01/05/52 as "The Mysterious Black Ledger"-  in Woman's Day, 03/31/52 and reprinted in EQMM 12/55)
• KIDNAPPING DEPT. -- "Child Missing!" (This Week, 7/7/51 as "Kidnaped!", reprinted in EQMM, 6/58)

All short stories, except were noted, are © 1949 to 1954. All are copyright to the United Newspaper Magazine Corporation and were apparently published in This Week.

The little stories collected in Q.B.I. show EQ's storytelling ability. Some of them involve very clever puzzle plots by any standards, such as "My Queer Dean!" and "Snowball in July". But even in minor pieces like "Cold Money", the reading is surprisingly satisfying. (Michael E.Grost)

In "Cold Money", the bad guy keeps renting Room 913 of a hotel; as Francis M. Nevins pointed out, this recalls a similar situation in Cornell Woolrich's The Room With Something Wrong (1938), which also involves mystery in Room 913. The house dick of the hotel plays a major role in both tales, as well. This is clearly a homage to Woolrich and one of his best stories. One suspects that EQ has added little homage’s and in jokes to many of his works, playful references to other mystery writers' stories; maybe they are as numerous as Alfred Hitchcock's cameo appearances in his movies.

In EQ, there is a situation, then some event occurs, and one is in a logical variation of that situation, and then another event takes place leading to a logical variation of the preceding, and so on. Even little pieces that are not triumphs of puzzle plotting can show this kind of unfolding in EQ. Maybe that is why many of EQ's short pieces are so much fun. EQ's radio play "The Adventure of the Mark of Cain" is a good example of this. Its use of a kind of logical analysis of a situation through progressive plotting is especially striking.

The stories in Q.B.I. deal more with the underworld than is typical of EQ. The stories move very fast and are quite compressed. Often this is done by humorously invoking clichés of underworld stories, films, and news accounts. The invocation is often done with wit and clever phrasing. Events are often more synopsized than dramatized, usually considered a second rate approach, but one that works beautifully here, partly due to EQ's skill with "le mot juste". This allows tremendously complex stories to be told in a small space. Even the detection often gets ingeniously summarized." (Michael E.Grost)

"The Yellow Ledger" aka "Ellery Queen's Greatest Case" a radio script broadcast on 12-17-42 or 12-19-42 was adapted "The Black Ledger" and collected here after originally being published in This Week.

Many of the tales focus not on murder, but on crimes such as robbery or impersonation. Three stories of 1951, "Driver's Seat", "Double Your Money", and "The Gambler's Club", all deal with ingenious swindles. "Double Your Money", and "Money Talks" (1950) portray poor, ethnic, working people in New York City, whereas "The Robber of Wrightsville" (1953) shows class conflict in the "typical" American town of Wrightsville. This is one of the most left wing of EQ's tales. Most of Q.B.I. strives for relative sociological realism. There is little overt surrealism, although the disappearances in "Double Your Money" (1951) and "Snowball in July" (1952) have their moments of magical strangeness. This realism might not have been entirely a matter of EQ's personal preference. By the 1950's, when these tales were published, Golden Age flamboyance was considered old-fashioned by most mystery critics. Realism was regarded as the most important trait of a detective story, and EQ obliged here. The series probably was modeled on William MacHarg's¹  The Affairs of O'Malley (collected 1940), which is a similar series of brief tales set against authentic New York City backgrounds, with "ordinary people" as characters. Some of MacHarg's tales, such as "Broadway Murder" and "Murder Makes it Worse", include swindles as well as murder, although EQ's approach to swindles is far more mathematical than MacHarg's.