The Checkmate Detective Agency is hired by the rich owner of a horse farm, after what appear to be bogus attempts on her life. This all happens after her husband is found guilty of murder and receives the death penalty.

A newlywed bride faces disaster when her new husband suddenly disappears, unknowingly at the hands of an escaped criminal trying to escape a death sentence.

Two car thieves run down an innocent man and kill him. That man's best friend wants to find the thug behind the two thieves, extract a confession and then execute him by cyanide.

Checkmate comes to the aid of a woman with a traumatic past when it becomes evident that someone is trying to make it appear she's mentally unstable. discrediting her eye-witness testimony at a murder trial.

A well respected archaeologist is about to murder a mysterious man, supposedly dead for many years. The doctor's fiancée hires the Checkmate team to stop the murder.

A wealthy heiress is trying to escape not only her money hungry relatives but also the criminals who want her dead before she testifies as a witness against them. The Checkmate agency steps in to help.

Whitney Thorne is an oil magnate who is being targeted by an ex-partner. His daughter hires the Checkmate agency to help prevent his murder, but Thorne wants a showdown with his nemesis.

Checkmate enlists the help of a Major in the Marines to prevent an action taken against the widow of a dead private, whom the Marines claim never lived.

Barbara Rush plays a dual role in The dark divide. Why should Margaret Russell's life be threatened? Her aunt keeps getting phone calls from a woman named Nikki Garnett, threatening Margaret. What motive could the woman have?

Jed is on vacation in Mexico and meets up with a beautiful woman. But when he arrives at the beach they planned to meet at, Jed finds her stabbed and bleeding in the sand. Of course, just as he pulls the knife from her chest, the police arrive, arrest him and charge the innocent man with attempted murder.

The daughter of an Ambassador with a history of speeding runs over and kills a Chinese child. She is not charged because of diplomatic immunity but soon she starts to receive threats from those in the Asian community. Checkmate is called in to provide protection.

Attorney Emory Olivant invites Corey, Sills and Dr. Hyatt to a party. Once all the guests have arrived, Olivant announces that they are going to play a game—a murder game in which he will be the killer.

Checkmate's housekeeper is thrown from a window. But before she dies, she calls Jed and tells him she heard one of her clients speak of an upcoming murder. Now Jed and Checkmate must find the one to be murdered and figure out who the killers are.

Reverend Wister, who has spent many years of service in China, is wounded in an apparent assassination attempt upon his return to San Francisco. He hires Checkmate to help him find a Chinese man of mystery, ostensibly to warn the man of an impending assassination attempt. The good reverend, however, proves to be a man of mystery himself

Arguably the finest episode of the series, featuring guest star Peter Lorre as an ex-con criminal mastermind determined to wreak revenge on master criminologist Sebastian Cabot. An intricate series of cat and mouse moves between the two geniuses culminates in a surprise and ultimately poignant ending, befitting the episode title. This episode stresses the close friendships between the three detectives of CHECKMATE INCORPORATED as it contrasts with that of the brilliant, but soulless Lorre. Directing, writing and acting are all exemplary.

A friend of Dr. Hyatt's, Judge Ralph G. Addison, has been receiving anonymous calls and letters warning that he will die if a man he sent to death row is executed. Checkmate's investigation raises questions about the condemned man's guilt, and the judge's character.

Jed and Dr. Hyatt go undercover as employees in a well-to-do household after Checkmate is hired by an anonymous client to protect the family from an unspecified danger. While there they encounter a grumpy housekeeper who hates beards, a woman who is about to marry for a third time, the woman's patrician uncle, her mysterious intended groom, and her high-spirited young daughter who imagines things, most of which are fantasy. Most. less

Television comedian and crusader Dan Whitman is advocating stricter penalties for drunk drivers, especially for a woman charged with two DUI fatalities. The woman's husband is an ex-mobster with powerful connections who wants Whitman dead. Whitman hires Checkmate for protection.

The checkmate team is being held hostage by a gang led by rogue gangster Joe Farrell, who is running from the mob. He demands that Don act as courier for his estranged wife and a fortune in stolen cash, or Jed and Dr. Hyatt will die. When Don discovers that one of Farrell's men plans to double-cross Farrell, Don tries to take advantage of the situation by pitting the two men against each other.

Ernie Stone, reformed and repentant thanks in part to Dr. Hyatt, is paroled after serving 20 years for his role in the Christmas Eve armed robbery of a novelty store that resulted in a crippling bullet wound to the proprietor. Immediately upon his release there is an attempt on Ernie's life, and suspicion at first falls on the now-dead proprietor's unforgiving son, Chuck Ellis, who has been harassing Ernie. Checkmate, however, suspects Ernie is harboring a secret that would shed new light on why someone would want him dead.

Rock 'N' Roll star Buddy Robbins (played by 1950s pop star Jimmie Rodgers) has been receiving chilling death threats, and his agent hires Checkmate to investigate. Jed goes undercover as an aide to Buddy. After someone fires a shot at Buddy, Jed discovers that the person who made the threats and the person who fired the shot are not the same person.

A woman claims her husband killed a male friend of hers and that she will be next, but her moody behavior, and her past as a psychiatric patient, make Don wonder if her story is legitimate. Don and Dr. Hyatt try a gambit to see who needs protection from whom.

A temperamental lady soprano, Lola Tuscany, has premonitions of her own death, and Checkmate is asked to help keep her safe. A series of publicity stunts, and Miss Tuscany's superstitious nature, leave the Checkmate team skeptical- until Don's car explodes just after he and Lola get out.

Althea Todd has become the most reviled citizen of Jericho, California after writing a novel that aired some of the town's dirty laundry, including a twenty-year-old unsolved murder. Her life is endangered when she begins work on a sequel, so she hires Checkmate for protection.

Steve Margate is a highly successful comic strip artist who plans to kill off his title character, O'Hara. Someone is trying to make Margate appear legally incompetent by appearing before him donned as O'Hara and apparently trying to kill him when he is alone, and Checkmate suspects it is someone who stands to take over the strip and all its financial benefits with Margate out of the way.

Lee Tabor is a daring but claustrophobic big game hunter and friend of Dr. Hyatts, who asks his help in finding out who's trying to kill him. Dr. Hyatt and Jed fly to Tabor's castle in the jungles of Malaya where they expect one of the guests is the culprit . The guests include Lee's estranged wife, Kay, and his girlfriend, Mary Lou Keyes.

A deaf mute schoolteacher runs to Don's apartment for protection from thugs after she lip-read a conversation they were having at a restaurant. She could make out only jumbled portions of it, but it was enough to make her a target for murder. Don stays at her side while Checkmate looks for her would-be assassins.

Ex-convict Griff Nolan is jealous because his wife Libby earns more as a magazine editor than he does as a mechanic. More domestic strife develops when Griff becomes jealous of Libby's boss Lewis Bates --- and buys a gun.

Ballerina Janine Caree calls Checkmate, ostensibly for protection from a shadowy man with underworld connections who at first appears to be an obsessed fan. Don and Dr. Hyatt, however, have to leave for Seattle, so they refer her to a trusted friend and colleague. When the colleague and the shadowy man turn up dead, they are led on a trail of intrigue and murder that leads right where it began.

Corey is onboard a cruise ship to protect a woman who claims that her husband is trying to kill her, but her odd behavior raises doubts in Corey's mind. Also aboard is another private detective who was hired by the woman's husband, ostensibly to protect her from herself.

While on the verge of giving a speech Dr. Hyatt is called away by a request to investigate a murder at the Deervale Military Academy. With Sills going undercover one thing leads to another and the investigation leads to smuggling.

Successful fashion designer Georgia Golden calls on Checkmate after attempts are made to ruin her business, and end her life. The suspects at first are her younger sister, whom Georgia raised and who's tired of listening to her, and a business rival who used to be Georgia's lover. The Checkmate team, however, may be barking up the wrong tree.

Checkmate gets the job of protecting recently-widowed, thrill-seeking Gloria Kenyon from her rich, vengeful mother-in-law, who believes Gloria arranged her son's death by parachute to collect his inheritance. The elder Mrs. Kenyon soon dies, but not before hiring someone to kill Gloria, an order which still stands.

Movie stuntman Joe Martinez is quick to anger. When a propman causes an accident, Joe takes a swing at him - and knocks himself right out of a job.

Status-seeking retired contractor Ernie Venable gets Dr. Hyatt's seal of approval for a new security system, but that doesn't stop someone from throwing a poisonous snake on his property in an effort to scare him, or kill him. The Checkmate team must contend with Ernie's coarse manners while they try to keep from getting pneumonia from staying in his frigid home to find who's responsible and protect him from the snake.

A patient with an overactive imagination at a hospital for the elderly asks Checkmate to investigate strange happenings at the facility, and a series of carefully planned "accidents" aimed at Anne Elliot, wealthy heiress and wife of the facility's director, Dr. Thomas Elliot, seems to corroborate her suspicions. In the investigation Don ends up as a patient himself after suffering an accident on the property. After his recovery his suspicions are aroused by what looks like more than a professional relationship between Dr. Elliot and the head nurse.