An ex-con hires Markham to find his daughter---whom he's never seen.

Markham flies to Honolulu to investigate a woman's claim that her husband is trying to kill her.

Two crooked cops pursue a small boy who saw them kill a gangster.

Markham becomes a target for an assassin when he is hired to impersonate mysterious international financier Max Bossman—whose enemies are numerous the world over— but Markham finds some pleasure in the assignment because he travels across Europe with Bossman's wife, Friday.

Markham goes to Hawaii at the request of an old Princeton classmate who thinks his wife is trying to murder him, but after he meets the beautiful woman he isn't sure who the intended victim is.

The plot concerns what happens after an investigator finds a woman chloroformed in his apartment. When Markham returns to his apartment he finds a woman chloroformed but before he can summon aid, three gun-toting kidnapers appear from another room to announce that Markham's apartment will be used for a hideout until ransom is paid.

Markham uses a fake jewel theft to smoke out a vital witness in East Africa.

An old friend asks Markham to help clear a woman suspected of murder.

Charged with murder: the victim's son.

Roy Markham finds himself on the trail of his strangest and dealiest quarry- a ship's first mate who has become infected with a deadly South Seas virus that threatens a plague.

Kitty Brady is sure the death of her trucker father was no accident.

Markham's nephew asks his uncle's protection when he visits an eccentric family.

An English girl with a large Swiss bank account is trying to keep her finances secret from her government.

Actress hires Markham to protect her from revengeful actor.

Markham goes to Portugal to investigate the death of an American beauty but meets a friend on the trail of a narcotics ring. Sister of beauty killed in mysterious explosion gives sleuth address book full of suspects.

Markham is called to Hollywood when a multi-million dollar studio is being sabotaged.

On vacation in Guatemala, Markham is asked to find a woman's vanished husband.

A Mexican boy is charged with killing an anthropologist.

A woman thinks her husband ran off with another woman and asks Markham to find him.

Counterfeit stamps are flooding the London rare-stamp market.

Markham invesigates the mysterious disappearance of a playboy whose wife believes she may have shot him while engaged in a strange duel with him.

Markham is drawn into a gem smuggling scheme when a nightclub performer comes to him for help escape a beatnik killer.

Markham is hired by a bank to investigate the fatal shooting of a top client.

Roy Markham is hired to reunite a young girl with her father, on adventures of international investigator "Markham." Unbeknownst, he is followed by two killers who know they will be led to their target.

Markham is hired by an insurance company to probe a series of gem thefts, but before he can get a clue, his best lead is slain.

A crank's bombing of empty buildings finally kills a man.

An ex-lawyer suspects that killers are trailing his daughter---to get back at him.

Markham's client: a Canadian industrialist accused of assault. The investigator flies to Quebec to clear the executive accused of beating up a pretty secretary.

Markham has to unmask a bogus medium who's intent on deceiving an old lady.

Private Investigator Markham goes to Paris to check on a lovely Spanish lady. Louise is the lady in question and she's very fetching. Markham is trying to locate a fortune stolen from a small country.

Markham goes after art thieves who murdered a museum guard.

The opener finds Markham worrying about an assassination attempt on Middle East's King Hassem on his arrival in the U.S.