Breck plays Clay Culhane, a gunfighter who becomes a lawyer after his brothers are killed in a shootout: a gunfight in which he himself was seriously injured, but survived. Realising that his life had to take a different direction, Clay hung up his gun and began to study the law. Based in the town of Latigo, New Mexico, Clay attempts to solve trouble through the law, but circumstances often force him to strap on his guns again. Other regulars include U.S. Marshal Gib Scott (Russell Johnson), a Reasonable Authority Figure who is suspicious of Clay, but generally gives him the benefit of the doubt, and Nora Travers (Anna-Lisa), who owns the hotel where Clay lives and who plays peacemaker between Calhune and Scott.
Black Saddle contains examples of:
- Beardness Protection Program: In "Client: Tagger", Tagger has grown a beard so the man responsible for sending him to prison won't recognise him as Tagger stalks him.
- Clear My Name: In "Client: Tagger", Culhane is arrested for committing a murder he was trying to prevent. He has to break out of jail and locate the elusive Tagger to prove his innocence.
- Grave Robbing: In "Client: Starkey", Clay and Scott exhume an unmarked grave in the middle of the night while attempting to unravel the mystery of a Town with a Dark Secret.
- The Guards Must Be Crazy: In "Client: Meade", the deputy Scott leaves to guard the prisoner immediately goes to sleep and is taken completely by surprise when the prisoner's mentor breaks in to free him. Made even worse by the fact that Scott had woken the deputy up when leaving, and warned him what might happen if he dozed off again.
- Idiosyncratic Episode Naming: In the first season, all the episode were titled "Client: X" where X was name of the person who hired Clay's services. This convention was dropped in the second, where only one episode uses the "Client: X" formula.
- Little Useless Gun: In "Client: Dawes", Maggie Dawes pulls a derringer on Clay, only to have Clay contemptuously slap it out of her hand.
- Mail-Order Bride: In "Client: Dawes", Clay defends a mail order bride who is accused of murder when he new husband dies in a seeming accident. Maggie Dawes mentions her husband having picked her out of a catalogue.
- Meek Townsman: In "Client: Meade", the only witness that can prove Clay's client innocent of murder is a meek Shopkeeper who allows himself to be bullied by the dead man's family into changing his testimony.
- New Old Flame: In "Client: McQueen", Clay is hired by his old employer Senator McQueen to get back control of his ranch. McQueen's daughter Susan—now married—is an old crush of Clay's.
- Rancher: In "Client: McQueen", Clay's client is a retired senator who owns the biggest ranch in Texas and who is being bilked out of his property by his daughter and his adopted son.
- Retired Outlaw: Clay Culhane is a gunfighter who becomes a lawyer after his brothers are killed in a shootout, a gunfight in which he himself was seriously injured, but survived. Realising that his life had to take a different direction, Clay hung up his gun and began to study the law.
- Shopkeeper: In "Client: Meade", a shopkeeper in Latigo is the only witness to a shootout, and the only person who prove Clay's client is innocent of murder. However, he is a Meek Townsman who allows himself to be bullied by the dead man's family into perjuring himself: a decision with tragic consequences for just about everyone.
- Take Over the City: In "Client: Travers", rancher Hannibal Pardee is either buying out or driving out everyone in the town of Latigo, so he can kill the town which he blames for the death of his son.
- Town with a Dark Secret: In "Client: Starkey", Clay discovers that no one in Latigo will talk when he starts asking questions about Ben Starkey. When he attempts to dig deeper, he finds two months worth of papers missing from the newspaper morgue. And then he and Scott find a body in an unmarked grave in Boot Hill...
- Trivial Title: Clay Culhane uses a distinctive black saddle when he rides. Others occasionally identify him by the saddle, but it otherwise has no bearing on the stories.
- U.S. Marshal: Gib Scott is a Deputy US Marshal who comprises the only law enforcement in this region of New Mexico.
- Wrongful Accusation Insurance: In "Client: Tagger", Culhane suffers no consequences for breaking out of jail, and assaulting the marshal in the process, in order to prove his innocence of murder.