M Squad hunts for a bomb before it blows up a hospital. Jonas Blecker, an embittered bank clerk who went to prison for dipping in the till to loan money to depositors down on their luck, wants to commemorate his 1st anniversary as a free man by killing the judge who gave him the maximum sentence. The judge is in Columbus Hospital for a delicate operation and he can't be moved.
When a well-liked retired couple is found brutally murdered, evidence points to their curmudgeonly neighbor. Lieutenant Ballinger is initially skeptical of his story, but thorough investigation reveals that things are not always as they seem.
Detective Ballinger is brought in to investigate the murder of night club owner Joe Dalio. The case seems open and cut with a suspect in custody, however Ballinger has just enough doubt to continue the investigation.
A bail bondsman's son is kidnapped to force his father to post an $80,000 bond for the release of a murderous extortionist. Lieutenant Ballinger finds himself on a dangerous high-speed boat chase when the culprit attempts to avoid trial (and a likely death sentence) by escaping to Canada.
Detective Ballinger is called in after what seems to be a professional hit on a desk clerk at a hotel. A witness identifies who may have done the killing, but Ballinger is concerned he can not find any connection for why the clerk should have been shot.
Ballinger is called in to investigate when a burning car is found with the body of a young woman bound with wire inside. The chief suspect, playboy lawyer Paul Crater, seems to have an air tight alibi. Ballinger needs to cast his net wider to solve this mystery.
Used car salesman Larry Colman has argument with Art Brunswick, a man who claims to the be the father of Colman's daughter. Colman unearths evidence Brunswick is not who he claims to be leading to a deadly altercation.
Harry Conklin is killed while on the way to a secret Senate hearing into stand over tactics in the trucking industry. Suspicion falls heavily on a rival Martin Bodie. It is up to Ballinger to fight through the silence and uncover the truth.
A woman and her baby are hospitalized after a group of bank robbers run them down during an escape. Ballinger wants the men for the robbery but more importantly he wants them to pay for what happened to the woman and her baby
A witness fingers the gangster who cut a rival in half with a shotgun blast, but the killer's alibied by a beautiful actress. The thesp is beloved in ChiTown and has a sterling rep that'll guarantee acquittal. Lt. Ballinger must discredit her story and find out why Tammy's lying for smarmy hood Sandy, who now controls the Loop liquor racket.
Ballinger is brought in when a robbery and murder occurs at an armory. He is puzzled by the list of weapons stolen including a bazooka and other heavy weapons. He knows they cant sell the weapons, so what is their plan?
When an "electronic brain" worth $2,000,000 is stolen and held for ransom of $300,000, Captain Grey and Lieutenant Ballinger devise an elaborate ruse that they hope will lead them to the computer and the thieves.
A badly beaten man is admitted to hospital. He does not have long to live and the police need to work fast to solve the mystery. The man appears unremarkable other than being an identical twin of Ballinger.
Conrad Brenner is found dead in an apparent suicide. As Ballinger continues the investigation it becomes evident that he's actually been murdered, when a personal diary can't be found, Ballinger realizes the truth of the case.
Ballinger is on a case involving threats against a visiting prince to Chicago. Mo one is taking the situation too seriously until a little girl accidentally finds the detonating device for a home made bomb.
Lieutenant Ballinger works to solve a series of armed holdups as a means toward the capture of shotgun-wielding Ma Phelan, who murdered a detective while helping her son Pete escape from police custody.
Ballinger is working a jewelry theft when he becomes convinced one of thieves is a clean skin amateur. He realizes by putting pressure on this individual he has a chance to crack the entire racket open.
Willy Nichols is due to testify in a narcotics investigation, although under police protection he receives a threatening phone call and suddenly disappears. Ballinger must find Nichols to save the case.
Accompanied by a female reporter, Lieutenant Ballinger investigates an elderly woman's charge that the man who robbed her store and killed a police officer was able to escape as a direct result of Officer George Maxwell's cowardice.
Sonny Bradley is charged with murder. Ballinger begins to investigate and quickly realizes something is not right about the statements from the witnesses, and starts see a much bigger game being played.
A bookkeeper is robbed and murdered at a circus. A clown named Laslo is identified as the killer. Ballinger and the rest of M squad have to deal with how Laslo could have committed the crime while performing in front of 5000 people in the main tent.