Widower Lucas McCain can fire a round with his specially modified Winchester in three-tenths of a second. Added to his high moral code and resolve enable him to help Marshal Micah Torrance maintain order in town while raising his son, Mark, on a ranch near North Fork, New Mexico.
Reformed card sharp Julia Massini now runs a respectable boarding house in North Fork, but Sid Fallon is threatening to reveal her sordid past unless she lets him turn the establishment into a saloon and gambling hall.
Rebecca Snipe is returning to North Fork after a long visit away. Before her stage left, she over hears a man saying he's going to North Fork to kill a big man with a big mouth. Upon Rebecca's arrival in North Fork, Mark is smitten with her and gets it in his head to play matchmaker between her and his pa. Thinking Lucas has intentions on their sister, the Snipe brothers come looking for Lucas to see if he measures up to their standard of being good enough for her.
Tiffauges, a wealthy and sadistic Frenchman, who is used to getting whatever he wants, decides he wishes to purchase the McCain Ranch. Tiffauges' lead man, Xavier, proclaims Lucas to be muy macho, and does not believe Lucas will give in so easily. Xavier and the other men are tiring of being subjected to Tiffauges' whippings and cruel treatment. Lucas plays on the men's longing for freedom to keep his ranch.
Ward Haskins guns down Joe Flecker, who has evidence that could be used to blackmail him. Haskins thinks the information was given to Lucas, since he brought Flecker to the doctor before he died. Stirred up by Haskins behavior, Lucas goes through Flecker's things, finding a wanted poster for Haskins in the sole of Flecker's boot. He also finds Doc Burrage drinking. Doc is discouraged because three children have died of an anthrax epidemic that he has the new serum for, but nobody is willing to allow him to administer it in time. Haskins rides out to the ranch and is bitten by Flecker's horse, which is now believed to have anthrax. Mark overhears about how anthrax always causes death and is worried because he had bitten by Flecker's horse, also.
Two hired hands of a wealthy cattleman, who has been using the ranch for grazing his cattle, demand that Lucas move out. When Lucas refuses, he is beaten and dragged and then the ranch house is burned down. They left Lucas and Mark with the burning house and rode off with Lucas' rifle. Leaving Mark to tend to the animals, Lucas tracks them down and confronts their boss, Mr. Jackford.
Micah Torrance, a once famous lawman, is introduced as a drunken derelict, who stumbles into North Fork. Micah, nursing an arm crippled in a gunfight, is hired by Lucas to help out at the ranch. Three outlaws ride into town looking for revenge against Micah. When they kill the sheriff, it's up to Lucas and Micah to protect North Fork. Micah becomes North Fork's full-time Marshal.
When their wagon breaks down, Mark and an injured Lucas are stranded in the desert.
Rumson, without even saying to whom he had sold his property, left the bill of sale with the bank and moved away from North Fork. Curge, who's highest offer was upped by $1,000.00 is upset because Rumson sold out to a "peppergut". The Argentez family who bought the place are from Argentina. Lucas arranges for Mark to hang out with Manolo, who teaches Mark to use the Bolas. Manolo is angered at anyone who shows interest in his sister, he believes she is only for a "Caballero". Her latest suitor, Ned Dunnell, has been found murdered and the townsfolk are quick to believe it was Manolo.
Dan Nowry, released from Yuma prison, arrives in North Fork intent on getting even with Marshal Torrance,who helped send him to jail.
When a horse dealer transporting a prize stallion stops in North Fork, two saddle tramps try to use trickery to obtain it.
After Mark contracts typhoid fever and has a vision of his dead mother, he no longer seems interested in getting well.
An ex-convict is blamed for a brutal crime despite his claims of rehabilitation.
The McCains try to be tolerant of their embittered neighbor Abel MacDonald, who tels Lucas to keep off his land and won't allow his son to become friends with Mark, but they decide he's gone too far when he won't allow his injured boy to get medical treatment.
When a rambunctious teenager wrecks a schoolroom, Lucas McCain, as a member of the North Fork school board, asks the boy's reluctant uncle to pay for the damages.
A sharecropper enters his colt in a horse race, hoping to win enough money to buy his farm from the owner, who has bet on Mark McCain's entry.
To keep his invalid mother happy, an outlaw forces Lucas and Mark to go along with a masquerade that he is the owner of Lucas's ranch.
Lucas welcomes his old friend Tom Birch, who once saved his life, unaware that the man is now a bank robber who is on the run with his gang.
An unfounded rumor causes North Fork's outspoken feminist schoolteacher to be attacked by a mob of angry townspeople.
When his employer begins to suspect him of embezzlement, bookkeeper Asa Manning decides to hire a professional gunman to take care of the problem.
U.S. Marshal Sam Buckhart arrives in North Fork in search of renegade Indians suspected of the brutal killing of a Texas Ranger and his family, but the townspeople are suspicious of him when they discover that he too is an Indian.
Lucas puts his life in jeopardy when he agrees to testify in a murder case where the first witness was killed before he could testify, and the killer is still at large.
When a rancher dies after the bank forecloses the mortgage on his property, his son blames the banker for his father's death.
Newly arrived gunslinger Al Walker throws a mammoth party at the saloon, keeping acting Marshal Ben Waller busy until Lucas is forced to intervene.
When Lucas hires an ex-con as a ranch hand, the man is the first one under suspicion when a robbery and murder occur in the area.
Lucas helps his former Army captain, now an undercover federal agent, infiltrate a gang of bank robbers.