Mike receives an emergency telegram from her sister Rebecca -- her mother is gravely ill. Mike rushes to Boston to her mother's side, the Cooper kids in tow, where Dr. Mike and her ""roughhewn"" children are met with raised eyebrows by Dr. Quinn's own family. While consulting with Elizabeth Quinn's attending physician, Dr. Mike meets a handsome and progressive Doctor, Dr. William Burke. Dr. Mike's prognosis of her mother (hepatitis) differs with Mrs. Quinn's doctor, Dr. Hanson, who diagnoses cancer. Dr. Burke, however, believes Dr. Mike may be onto something. They have a lot in common and develop a strong mutual admiration for each other. They work together to cure Mrs. Quinn and some of Dr. Burke's other patients. Meanwhile, Matthew chafes at being stuck in Boston away from Ingrid, while Colleen appreciates the learned and cultured atmosphere and Brian adores the candy stores. Just when everyone has settled comfortably into the Boston routine, Sully shows up, unannounced and in buckskin

Sully arrives in Boston and discovers that he's facing worthy competition for Mike's affection in the form of Dr. William Burke. Sully at first settles uncomfortably into Mike's Boston surroundings, but later, with prodding from the kids, submits to a grand makeover. Later, Sully romances Mike with dining and dancing, even attending an opera together. At an all-male medical society, Dr. Burke steps aside so that Mike can present a paper on Indian medicine, while Sully looks on. Afterward, Sully overhears Dr. Burke proposing marriage to Mike and heads back to Colorado, but not before confessing his love to Mike. In the end, Mike declines Dr. Burke's marriage proposal and Mike and the kids return to Colorado, where Dr. Mike returns Sully's declaration of love with a vow in kind.

Mike and Sully go to the Reverend for a dose of preventative pre-marital counseling, and recall the path of their romance.

Mike's mother arrives with elaborate wedding plans; Custer puts a bounty on best man Cloud Dancing.

While Sully is off thinking and doesn't return for several days, Mike gets worried. Although Mike continues to believe in their love. When Sully finally returns, Mike realizes she just wants Sully as her husband. Mike and Sully marry on May 20, 1870. Brian, feeling left out, has a surprise for the newlyweds.

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.

After Marjorie joins the Women's movement she blows into town stirring everyone up and has a fling with Loren.

Marjorie brings a group of Temperance Women (opposed to alcohol consumption) to C.S. Jake goes on a dangerous drinking binge, when he thinks Hank and Teresa are seeing each other. Grace begins to drink heavily to numb her grief. Robert E. moves out.

A diptheria epidemic sweeps through C.S. Michaela performs a procedure that is not a proven cure. Becky (Haylie Johnson) dies.

Mrs. Quinn wants to take to the children to Boston with her. She also disapproves of Loren and Marjorie's relationship. Marjorie contracts the illness. The family sneaks Sully home for Thanksgiving.