Originally Aired: November 2, 1958

Gunsmoke #343, "Old Man's Gold," begins when Cassius Mayhew arrives late at night at Matt Dillon's office with an unusual request. His wife is gravely ill, stranded in Dodge City on their journey west to find a dry climate for her health. While asking Matt to fetch Doc Adams, Mayhew also leaves a mysterious suitcase filled with family treasures for safekeeping in the marshal's office. The situation grows complicated when Henry Brayles appears, claiming to be Mayhew's brother-in-law and demanding to see what's inside the suitcase, accusing Mayhew of stealing family property.

Tensions escalate when Brayles attempts to force his way into Mrs. Mayhew's hotel room to confront his sick sister. Matt must intervene when Mayhew pulls a derringer to protect his wife from the intrusion. With Doc Adams confirming that Mrs. Mayhew is too ill to travel or receive visitors, Matt finds himself in the middle of a bitter family dispute. As suspicions mount on both sides about the true contents of that locked suitcase, the marshal must determine who's telling the truth and what's really at stake.