Brian's homework assignment, an essay entitled, ""What Is Love?"" to be written in honor of Valentine's day, coincides with Dorothy and the town's production of ""Romeo and Juliet."" Also, Becky and Colleen compete to play Juliet, Dorothy and Jake split up, and Sully gives Mike an engagement ring.

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.

The honeymoon is over for Mike and Sully as the newlyweds must adjust to life in a changing Colorado Springs where a bullish Boston Brahman named Preston A. Lodge III establishes the towns first bank. Preston Lodge III: Jason Leland Adams.

The town invites a traveling all-star baseball team for a fundraising event, but later suspects that they have been swindled. Otis James: Joel Anderson.

As Colorado Springs prepares for Christmas, the family receives a rambunctious toy poodle from Mike's mother in Boston, and Brian has a case of puppy love for a new girl in town. The Rev. Johnson recruits folk for a Nativity pageant. Sara Sheehan: Jann Michaels. Mrs. Sheehan: Susanna Thompson.

Sully pursues a renegade mountain man who has kidnapped senator Leonard's son, in protest of the Senator's support of Colorado statehood. Meanwhile, Mike is forced to stop her practice when her schedule threatens her pregnancy. Ezra Leonard: Lawrence Pressman. Noah McBride: Denny Miller. Dr. Cassidy: Jerry Hardin.

The rescuers get ugly after Leonard offers a bounty for the mountain man, so Sully sets off alone.

A renegade stabs Cloud Dancing, and Emma has a tumor, so Mike cannot slow down before the baby is born.

Dr. Mike prepares for the birth of her baby. Mike's family arrives for the impending birth of Mike and Sully's baby, bringing along a new young doctor (Brandon Douglas) to help deliver the baby. Meanwhile, Sully is hurt while trying to rescue Cloud Dancing and others from Sgt. O'Connor (Patrick Kilpatrick) and his patrol.

Wounded Sully must deliver Mike's baby. Dr. Cook is forced to perform a major operation. Katie Sully: Alexandria, McKenzie and Megan Calabrese.

Dr. Mike, Sully and Matthew team up with a legendary marshal in order to nab the thieves who wounded Matthew during a bank robbery.

As Christmas approaches, Brian questions his faith when he learns that Dr. Mike cannot save the sight of the Reverend.

When Colleen, who is working on a college paper, asks Dr. Mike to recall her most memorable case, Dr. Mike looks back on the five turbulent years she's lived and loved in Colorado Springs. As they sit with Andrew, who is mysteriously ill at the clinic, Dr. Mike reminisces about her tumultuous career -- its successes and its failures -- and realizes how many divergent cases she has seen and treated.

When Andrew's condition takes a turn for the worse, Dr. Mike warns Colleen about the fine line between emotional involvement and professional detachment, an issue with which she has long struggled in the frontier town that's now her home.

Sully arranges an escape for Cloud Dancing, leading him and the Indian to become wanted men.

Everyone is doting on Katie and Brian feels slighted. Brian receives a letter and picture from his real father, which leaves him feeling like he doesn't belong anywhere. Brian starts behaving badly. He gets Anthony to skip school with him and they hop a train. Sully punishes Brian. When Brian questions Sully's actions, Sully says that he is doing it because he is his Pa.

Sully is found alive, but badly hurt. As Michaela nurses him back to health, she keeps him hidden from the army. Sully sneaks into the homestead one night to spend time with his wife.

Sully and Michaela are on their way home for Christmas, when they stop to help a couple inexperienced in the wilderness.

Michaela is shot at the clinic by a man that has a grievance with doctors. The physical wounds heal, but the emotional ones linger.

Dr. Mike's elation at Colleen's acceptance to medical school quickly turns to disappointment when Colleen chooses to marry Andrew instead. A bitter family argument erupts when Dr. Mike tells Colleen that she is less than overjoyed at her announcement and feels that the couple is rushing into marriage and should wait until Colleen completes medical school. Meanwhile, Robert E and Grace have wonderful news to share; the stock market crash hits Preston and the townsfolk hard; and Dorothy and Cloud Dancing reach a new level in their relationship. As part of the Network's 50th Anniversary celebration, classic footage of James Arness as legendary Marshal Matt Dillon of ""Gunsmoke"" is digitally integrated into this episode. When Jake breaks the news to Hank that he's accepted Preston's offer to buy his share of the Golden Nugget that would make him partners with the despised Preston,