Abby asks Colt for space, but he finds every excuse in the book to drop by. Luke and Mary tie the knot in Vegas. Lisa Neumann accuses Colt of theft.

Back in Colorado, Luke works to win back Colt and Beau's trust. Abby invites Colt to a teachers' mixer. Mary struggles to stay clean.

Beau gives Colt a taste of his own medicine. Mary asks Luke for help paying the mortgage. Colt confronts Abby about not getting to see Peyton.

Joanne shares difficult news with Beau. Abby helps Colt with a business idea. When Mary goes missing, Heather takes drastic measures.

At Colt and Luke's encouragement, Beau and Joanne plan a celebration. Abby asks Colt to go to counseling. Mary's downward spiral continues.

Colt asks Abby to lie to the police. Joanne and Beau have a heart-wrenching talk about the future. Mary tells Luke she wants to go to rehab.

Abby and Beau pressure Colt to take Lisa's deal, but support from the local ranchers leads him to waver. Stress causes Luke to lash out.

Colt tries to round up the other ranchers to give Neumann's Hill some competition. After another argument with Abby, Colt signs the divorce papers.

Colt, Beau and Luke bond during a road trip to New Mexico. Back home, Abby runs into Mary and Nick.

Luke, Colt and Beau find Mary in bad shape in Nick's trailer. While Luke brings Mary back to the ranch, Colt and Beau wait for Nick.

To celebrate their last Thanksgiving on the ranch, Colt and the guys go on a turkey hunt. Mary checks into rehab.

Abby invites Colt out for a birthday dinner ... which might be a date. But the plan goes off the rails after Colt has an argument with Luke.

As Colt battles the elements, he leaves Abby a poignant message. Armed with a new perspective, Beau surprises Joanne.

Colt finally wins back Abby's trust -- but he's afraid to tell her he knows who killed Nick. Beau and Joanne look for a house together.

Maggie returns from Florida with news. When Dale uncovers a problem with the herd, Colt weighs whether to tell Lisa Neumann.

Luke urges Mary to go back to rehab. The police find a gun near the trailer and make an arrest, leaving Colt struggling with his conscience.

Luke's friend from the service offers him a job. Meanwhile, trouble brews with the co-op. Maggie tells Beau that she's met someone new.

Jerry warns Colt that Lisa Neumann has a good case against him. And when Luke bails on work, Colt has to miss Peyton's baptism.

In the series finale, Luke opens up about his struggles, Maggie throws one last Christmas party at the bar, and Colt gives Beau a heartwarming gift.