Horror mounts when a flu epidemic attacks Colorado Springs. Dr. Mike must attend the sick townspeople and protect others from getting the deadly disease. But being a lady doctor has people questioning whether she can handle the fatal epidemic.

Mike's estranged mother (Jane Wyman) visits, but she and Mike are still miles apart. Meanwhile, Robert E is injured in a fire.

A gunslinger (Johnny Cash) arrives looking for a quiet town in which to hang 'em up, but Colorado Springs is itching to lynch an immigrant (Christopher Keene Kelly) for cattle rustling to feed his starving family.

A bitter Loren, who blames Sully for his daughter's death, tries to repossess Dr. Mike's cabin when he learns he still owns the deed.

As Dr. Quinn is trying to persuade the townspeople that smallpox vaccinations are necessary, the father of Brain, Colleen, and Matthew arrives.

When several townspeople come down with mercury poisoning, Dr. Mike forces a reluctant Sully to guide her to the high mountain stream which may be the source of the problem. The trek is difficult for her, but she ultimately earns Sully's respect and gratitude after saving his life twice despite a broken wrist. Just as they confirm that the water is being polluted by a local mine owner whose mining process is dumping mercury into the stream, they are captured by his men. In the interim, worried townsfolk send out an inept posse to try to locate Sully and Dr. Mike. Olive backs Grace's new venture -- Grace's Cafe. In the end, Dr. Mike saves the day by curing the mine owner's son, who has fallen victim to the poisoned water, and convincing the owner to close the mine.

Dr. Mike tries to heal the soul of Doc Eli, a Civil War surgeon turned patent medicine show huckster, who's come to like the taste of his own medicine, an all-curing elixir used by the fabled Kickapoo Indians. She doesn't trust the sales pitch of this exploitave medicine show man, especially when she's facing a real medical crisis involving Myra. She must help Doc Eli face his past demons, before he can help her remove an ovarian cyst from Myra, in a technique he pioneered. Meanwhile Sully's on a similar mission in trying to convince Franklin, a disillusioned Cheyenne, survivor of a massacre, to join his own people in their continuing fight for survival. Myra and Horace get engaged.

Sully ends up badly beaten and partially paralyzed following a run in with buffalo hunters who were hired by the railroad to clear the buffalo and Indians out of the planned train path. As Dr. Mike, Cloud Dancing and the kids fight to help Sully regain the use of his legs, a con man who's passed himself off as an advance man for the railroad is in the process of swindling the townsfolk out of the deed to their property. Sully recovers and Dr. Mike unmasks the con man's plan thereby saving the townsfolk's property.

After ambushing Black Kettle's camp, General Custer enters the town carrying wounded soldiers and Indian prisoners, including Cloud Dancing, whom Custer threatens to kill if Dr. Mike does not treat his men before the injured braves. Later, Dr. Mike treats Cloud Dancing's broken arm while he remains shackled in the livery after Custer's interrogation. When Custer jokingly hauls Cloud Dancing before a firing squad that fires blanks, Dr. Mike and Sully engineer Cloud Dancing's escape. Meanwhile, Olive opens a Hurdy Gurdy, recruiting girls from the immigrant camp and a reluctant Loren, Horace and Jake for the band. Matthew buys all of Ingrid's dance tickets then shyly confesses that he doesn't know how to dance. Robert E. and Grace exchange looks. Robert E. is still burned from The Visitor (#3).

Matthew's sudden announcement that he wants to marry Ingrid causes upheaval in his relationship with Dr. Mike, who feels he's too young. In an effort to prove he's man enough to make his own decisions, he convinces Sully and Cloud Dancing to allow him to partake in a four-day Cheyenne ritual. This is the final straw for Dr. Mike, and she confronts Sully before she storms off looking for Matthew. Meanwhile, Ingrid suffers asthma attacks, and her treatment is undermined by Dr. Mike's disapproval of their marriage plans. Dr. Mike comes upon Matthew going through the rite of passage and seeming at peace with himself, so she lets him finish uninterrupted. Later, Dr. Mike and Matthew resolve their differences, with him deciding to delay the wedding and her giving Matthew her engagement ring for Ingrid.

Colleen develops a teenage crush on Sully after he pulls her out of the path of a runaway wagon. Imagining herself as a damsel in distress and Sully as her knight in shining armor, she purposely sets out to get lost in the woods hoping Sully will rescue her. A freak cold snap blows up and she almost freezes to death before Sully and Dr. Mike find her. Dr. Mike works hard to save Colleen's badly frostbitten hands, and Sully ultimately has a heart-to- heart talk with Colleen. Meanwhile, racial tensions in town reach a boiling point when Hank accuses Grace of food poisoning which is later proved false when Dr. Mike discovers Hank has been eating meat infected with trichinosis.

While Brian and Sully are out hiking, Brian climbs a tree and jumps out before Sully can stop him. Brian lands hard, hitting his head. Mike, angry with Sully for not watching Brian more carefully, is relieved to find no signs of injury. Later, the townsfolk argue over who will build the new schoolhouse, Matthew wants Robert E included, but, in the end Jake and Loren are tapped for the job. Brian begins to exhibit symptoms of compression, which escalate to blindness and later, coma. A specialist can't be found and Mike must perform a dangerous brain operation while Jake and Grace assist. Meanwhile, the town, including Robert E, pulls together to build the schoolhouse. Brian awakens and wanders out to the new school where Mike and the family find him, overjoyed that he can see again.

When Mike and Sully stop to check on old Mrs. Johnson, they discover her dead and a young boy, Zack, hidden in the closet. Mike takes the child in and confronts the townsfolk, who reluctantly admit to knowing the boy's mother was one of Hank's whores. When she died they sent Zack to Mrs. Johnson because he was ""simple."" Mike is frustrated in her attempts to find a medical diagnosis and cure for Zack's condition. Mike's further detective work reveals that Hank is Zack's father, and she helps Hank own up to his responsibility. Meanwhile, Brian seems to be the only one to get the boy to exhibit his artistic abilities, and he is mistakenly given credit for a drawing that Zack has done. Later, when Zack's artistic talent is discovered, Hank agrees to send him to an art school in Denver. The show has a cute opening scene of Mike and Sully with him criticizing her driving.

David Watkins, a civil war photographer arrives in Colorado Springs. Dr. Mike diagnoses David's diabetes and is frustrated that he refuses treatment and will ultimately go blind. David suggests taking a portrait of the town and an argument ensues over who will be in it. When the camera equipment is destroyed, the whole town must pull together to create a camera and take the photo before David's eyesight fails. At the same time, Mrs. Bing, Horace's mother, is brought to town, seriously ill. Mrs. Bing disapproves of Myra until she learns how much they love each other, and on her deathbed bestows her blessing on their marriage.

Dr. Mike takes in Red McCall, a down-and-out cowboy, and his ailing half-breed infant child. McCall reaches the end of his rope trying to care for his baby, so after robbing Loren's store, he leaves the baby in Michaela's care, sensing she could find a suitable home for his child. Dr. Mike's attempts to find a home for the baby prove futile. When she travels to a remote cabin to check on the health of it's owner, she finds him badly mangled from a bear attack. Her horse is frightened off by the bear, and she's marooned in the cabin until Sully shows up looking for her. They narrowly escape being the rabid bear's next victims. After returning to town, Dr. Mike decides she'd rather raise the child herself than turn him over to an orphanage. However, Sully locates Red and convinces him to keep the child.

When teen-outlaw Belle Starr robs the saloon, Mike takes her in, intending to reform her; Colleen overcomes her fear of riding. Belle Starr: Melissa Clayton.

A paleontologist arrives in town, igniting ""bone fever"" among the townsfolk when he announces that dinosaur bones are worth money. Meanwhile, Matthew and Colleen try to prevent Brian from discovering that the ""dinosaur"" bone given him by his pa is fake.

With no child-protection laws, and influenced by Charles Darwin's theory of evolution, Mike has a girl removed from her ""guardian"" by taking the man to court and trying him for animal abuse. Mary Ann: Doren Fein.

Catherine, a beautiful blond woman captured by and raised with renegade Indians, is brought to Colorado Springs by soldiers when her tribe, which includes her husband, is wiped out, leaving her the sole survivor. She initially earns the townsfolks' sympathy, then their contempt when she rejects their gestures of kindness, doesn't know the language, and falls down into an epileptic fit. Indeed, her Indian name was ""Shivering Deer"" thanks to her grand mal epileptic seizures. Mike takes her in, but the only members of the family she trusts and feels comfortable with, especially with her faltering English, are Sully, then Brian. Brian, however, becomes decidedly less enamored of her when he accidentally glimpses Catherine kissing Sully. Later, when Brian confronts Sully, he doesn't understand Sully's distinction between ""being kissed"" and ""kissing someone,"" and troubled, tells Mike about it. Meanwhile, Jake, in a conversation with Loren and Dorothy about what marauding Indians do to white

Eight orphans arrive on the train. The Reverend takes them in at the church and Mike nurses their ailments. When no one in the town wants to adopt the orphans, the Reverend extends a proposal of marriage to Mike so that they can raise the orphans together. Mike briefly considers the offer, and Sully confronts her about it, asking her if she loves him. She accuses him of not making any kind of committment to her, whereas the Reverend has, to which he replies, ""If marriage is all you want...."" leaving his meaning clear without being spoken that he's possibly willing to offer more. Considering this, Mike turns the Reverend down, much to the relief of Sully and the Cooper kids. Eventually, the orphans board the train and leave town, but each orphan boards the train a more complete person as a result of their interaction with the townsfolk. Dr. Mike confronts the fact that she can't save the world and she and the Cooper kids emerge as a more united family.

A ragtag circus, consisting only of Heart and Atlantis, a mother-and-daughter team, arrives in Colorado Springs. Heart, the mother, enlists the townsfolk to participate as performers. Everyone accepts but Mike, whom Heart tries to engage as a trapeze performer. Later, in the homestead, Colleen reveals her fear of being in the limelight, and Brian asks Sully if he'll perform on the trapeze, per Heart's request. Sully says to Mike, ""I will, if you will,"" upon which Mike says she'll perform if Colleen will. Colleen reluctantly accepts the challenge. Heart engages the Reverend to be a magician, with Miss Dorothy as his lovely magician's assistant. Brian and Loren are the designated clowns. Colleen, Atlantis and Matthew do a tightrope act together, and Jake is pressed into service as the ring announcer. The town happily embraces their various roles in the circus, but friction occurs between Mike and Heart when Mike discovers that Atlantis, Heart's daughter, has webbed fingers. Mike wants to

A troop of black cavalry soldiers ride into town intending to cover themselves in glory by eradicating hostile Dog Soldiers who've been attacking the railroad. Mike commits an act of civil disobedience by tipping off the Indians, which results in carnage on both sides and the defeat of the Buffalo soldiers. She's accused of treason, and jailed, but the arrogant black cavalry leader, Sergeant Zachary Carver, manages to exonerate her when he's made to realize, through the combined efforts of Sully and Mike, that his beloved troops are nothing more than pawns in the U.S. Army's policy of genocide against the Indians. Returning the favor, Mike manages to medically fake the Sargeant's death, and he escapes court martial. Meanwhile, Colleen cheats on a test and by doing so manages to win a school trip to Washington. Mike must then explain the concept of ""good lying;"" that is, civil disobedience for a principle, and ""bad lying,"" that is, Colleen's self-serving actions regarding the test. In t

An elderly man comes to town with hopes that the natural spring will help his rheumatism. Dr. Mike can't convince Sully to plan for the Halloween festivities.

When Julius Hoffman rides into town and engages Matthew in a poker game, Matthew thinks he's found a great way to earn money to finish he and Ingrid's homestead, although Mike and Sully disapprove. At first, Matthew wins steadily, though he and Ingrid get into a terrible fight when, after missing an elaborate dinner she cooked for him (he was in a game), he confesses he used her hard-earned laundry money, which she gave him for building supplies, as a stake. Though Ingrid and Mike disapprove heartily, Matthew continues playing the game, even after he gets beaten up and robbed of his earnings. Eventually, townsfolk become so confident in Matthew's abilities that everyone but Mike, Sully and the Reverend back Matthew in the big poker game. The Reverend pulls Mike aside and confesses that he was once a gambler, knew Julius, and suspects that the town's been set up. As Matthew makes his way to the big game, Ingrid breaks up with him over his poker playing. In the process, she returns the e

Mike and Jake go head-to-head when both campaign for the Mayorship of Colorado Springs. At issue: whether drinking and prostitution should be outlawed. Myra finally breaks loose from Hank.