A friend and comrade of Frank is believed to have committed suicide.
Cannon receives a confession from a dying hitman who says he was responsible for the murder of his wife and daughter 14 years ago.
Frank Cannon and Barnaby Jones team up for an investigation of a murder at a big corporation in which a deliveryman was charged with the crime.
Cannon investigates a doctors claim that he is innocent of a death he was charged with concerning a patient he was treating that had slipped into a diabetic coma. Cannon becomes involved in a medical malpractice suit when a young resident physician is charged with making the wrong diagnosis on a woman in an apparent diabetic coma who dies after his treatment. Hired by the hospital facing a two million dollar suit, Cannon hears testimony of the accused Dr. Jeff Reston, played by guest star David Birney, that the woman he treated wore a diabetic's bracelet. She was, in fact, suffering from hypoglycemia. But the bracelet disappeared and none of the nurses attending with Reston can back up his story. Reston then gives Cannon a motive for a possible conspiracy against him.
Cannon reopens an investigation when he discovers a convicted man may be innocent, but then refuses parole. Robert Foxworth is the villain. He plays a murderer, an ex-Green Beret who served in Vietnam with overtones of CIA activity. The murdered man was Cannon's friend, and that brings him into the case. When the convicted murderer turns down a parole, Cannon becomes very curious.
Cannon investigates the story from a beaten woman who's friend, a famous pop singer, has disappeared somewheres in the Hollywood Hills area.
With the help of his former police partner, Frank is asked by his former captain to reopen a case of a corrupt cop who has reappeared after being declared dead years ago.
A group of terrorists have drugged Cannon with a poison, giving him 72 hours to give them a defector and receive the antidote or die.
As a last request, Frank's former police mentor has asked him to go to Mexico and retrieve his son.
Cannon has been hired when a VP of a petroleum company is charged with misappropriation of funds and faces dismissal and prison time.
Cannon investigates when an heiress finds an ax buried into the head of a snowman outside of her home.
Cannon is asked to find out if a judges fiance is responsible for him being compromised.
Frank investigates the death of a gang member, who seems to have been killed by the son of a General and war hero..
Cannon is sent to investigate when a black community leader is murdered, just as he was to reveal a wrong doing.
Frank is hired when the son of a former Hollywood movie star suddenly disappears.
Frank Cannon finds out that Terry is pursued because of some snapshots he took. With the help of the photos Cannon gets in the dark zone between organized crime and high politics. And this becomes extremely dangerous for him.
Cannon is hired when the only witness to a robbery is a young child who blames an Arabian heir for the crime.
Cannon is hired when a crusading newspaper editor is found near a dead body, while drunk and unconscious in a hotel room.
The accountant of Eden corporation has disappeared. And along with him three million dollars. Does unscrupulous branch manager Sheffield have have to do with the plot? Cannon comes across a discovery and suddenly local reporter Julie Foster also plays an important role.
Cannon is haunted by the memories of his time in the Korean War.
A kidnapping with shady overtones compels a millionaire to hire Cannon for the investigation.
Cannon investigates the mysterious death of a scientist who was killed by a laser beam.
Cannon investigates when a former hitman seems to now be on someones wanted list.
Cannon investigates the shooting death of the girlfriend of a former basketball star.
Cannon is hired by the wealthy family of a young man, who is assumed to have died from an accidental death in Acapulco.
Cannon is hired to investigate when an Army researcher seems to have gone insane for no obvious reason. Another cry for help comes out of Cannon's past. A girl he once knew is concerned about her husband's -he's a research scientist- fits of irrational behavior. they touch on mind-boggling drugs here, a topical subject.