When Thomas's childhood friend and Naval comrade Dan Cook turns up dead, Thomas is adamant that the official cause of death, a burst bag of smuggled cocaine, is bogus, and enlists the aid of Dan's sister Alice in taking on the Navy to uncover the true nature of the top-secret assignment Dan was working on before his death.
A private investigator who works when he wants, lives in a beachfront estate in Hawaii, drives a posh Ferrari, runs up an unlimited tab at a swank bar, and charms attractive women in peril - that's the lifestyle of Thomas Magnum, aka Magnum, P.I.
When Thomas's childhood friend and Naval comrade Dan Cook turns up dead, Thomas is adamant that the official cause of death, a burst bag of smuggled cocaine, is bogus, and enlists the aid of Dan's sister Alice in taking on the Navy to uncover the true nature of the top-secret assignment Dan was working on before his death.
Magnum and Alice continue in their quest to find out the truth behind Lt. Dan Cook's death, and find themselves uncovering a case of gold smuggling, and a criminal mastermind whom Magnum and Dan once knew in Vietnam. But in trying to find out what really did happen to his deceased friend, Magnum puts his own life on the line as someone tries to stop him from investigating, using any means necessary...
Magnum is hired by a beautiful Chinese antiques dealer that he's making a play for to protect a precious ancient vase—The Soul of Sung—until its buyer arrives in Hawaii to collect it. But unbeknownst to him, the priceless ornament is wanted by a Tong gang from the girl's home country, and a deadly martial arts assassin who can kill in the blink of an eye is hot on the trail.
It's the Christmas season, and against his better judgment, Magnum agrees to being hired by five young schoolgirls to find their teacher, who has seemingly gone missing after falling in love. While he's working on the case, Magnum manages to convince Higgins to let the young girls stay on the Masters estate, but he's unaware that he's being deceived in a scam over a valuable painting recently purchased by Robin Masters.
Magnum returns from a case to find that Higgins' old Army commander is staying on the Masters estate, under tight security, until some I.R.A. members he helped capture are tried. Two secret intelligence agents hire Magnum to protect the brigadier and foil assassins out to kill him before the terrorists' trial, but the “need to know” basis the agents insist on operating by only serves to complicate matters for Magnum.
When a beautiful model-actress is killed by a shotgun blast in a scenario closely resembling a scene from the script of an upcoming film, it is seemingly suicide. Magnum is hired by her former producer and lover to investigate any other men that she may have been seeing before her death.
When Saul and Lena, an aging couple who run a local shop, abruptly make plans to leave town, suspicious Magnum and Rick, who are friends with the couple, investigate.
Higgins volunteers Magnum's services to guard a wealthy socialite's quarantined dog after the attempted dognapping of the canine. Sir Algernon Farnsworth soon finds himself to be the most wanted dog in Hawaii when his former owner, aging gangster Victor DiGiorgio, needs to get him back.
Although Eric Tobin was reported missing in action over eight years ago, his fiancee, Laura Fraser, endowed with ESP, doesn't believe it. Magnum befriends her and, in finding out the truth about Tobin, discovers that he was a highly trained and effective government agent working under the control of a man known only as Delta One.
Magnum is hired by a Supreme Court nominee to find the woman he married on the eve of the raid on Pearl Harbor.
Rick is organizing a surf-ski competition to be held at the King Kamehameha Club (much to the disapproval of co-committee member Higgins) when a Kahuna appears and places a "curse" on the club and all who use it.
T.C. makes a late-night flight to land on a tanker, but on the journey back he is cornered and arrested by the Coast Guard for transporting drugs. Magnum and Rick are certain of their friend's innocence, but are shocked when he intends to accept the charges and refuses their help.
A bubbly young woman hires Magnum to find her father who, after being missing for over ten years, had sent her a postcard from Hawaii. But her father is involved in some rather shady business, and Magnum isn't the only one looking for him.
A woman hires Magnum to protect Norman, who is facing kidnap unless she pays a ransom; but the case has some unexpected twists.
Having once been hired by wealthy, blind Agatha Kimball to find her missing granddaughter, Amy, Magnum's services are once again called upon by his elderly friend after she has been contacted by a blackmailer claiming to have some important information about Amy.
Magnum has been hired by a woman to act out some of her rich, bored sister's fantasy dramas, concocted from 1930s Dashiell Hammett films. Although growing to enjoy the world of fantasy, Magnum has a hard time keeping up with the eccentric woman, and when he finds out that her husband is a wealthy, infamously jealous and bad-tempered business man, he decides to cut his losses and end the arrangement.
Magnum tries to impress a beautiful 'fan' of Robin's by showing her the Robin Masters estate, only to learn that she is actually a top security expert hired by Robin to test the estate's security.
Magnum is hired by Barbara Terranova, a financially broke woman who can only afford his services for one day, to find her missing fiancé Roger. But the case has several tangles in store when Magnum finds there are others searching for Roger, too.
