Cullen awaits the birth of his baby, laboring under The Swede's thumb at Fort Smith. Durant deals with the fallout from a railroad accident.

As Cullen plans an exit from Fort Smith, he challenges The Swede; when a new adversary arrives, Cheyenne feels his presence.

Cullen goes back to work on the railroad and butts heads with his new boss. Durant and Campbell battle over a valuable piece of real estate.

Cullen deals with trouble at home as he takes railroad matters into his own hands. Campbell makes a move against Durant and Mickey.

Cullens's family is at risk when a stranger arrives, stirring up old feelings; The Swede faces the consequences.

Following an attack by a bear, Elam struggles to survive in a Comanche village and find his way back to Cheyenne.

Cullen attempts to reconnect with Elam upon his return. Durant takes matters into his own hands while putting an old problem to rest.

Cullen makes a decision to ensure his family's safety. Campbell hires a new federal marshal to clean up the streets.

Cullen goes head to head with the new marshal to recover his arrested railroad workers. Campbell confronts Louise over a story.

Cullen, Durant, and Campbell try to negotiate a settlement on how the streets will be policed. An act of terror strikes Cheyenne.

Cullen and Durant fight to save the life of a criminal. Meanwhile, Louise tries to provide support as Ruth copes with a great loss.

Cullen grapples with Ruth's unexpected decision; Louise jeopardizes her reputation to fight for a story she believes in.

As the railroad prepares to leave Cheyenne behind in the Season 4 finale, Cullen returns to Fort Smith to retrieve his family.

Cullen is in California with the Central Pacific Railroad, and must deal with the new workers.

Cullen and Fong find themselves in peril as they transport a locomotive over the Sierra Nevada mountains. The Swede gains Phineas' trust.

Cullen contends with violence in Chinatown set off by disgruntled railroad workers. Meanwhile, the Swede manipulates Phineas in his plot against the Mormons.

Cullen solves a Chinese labor strike in the wake of violence. Meanwhile, Durant pulls Mickey deeper into Union Pacific business.

Unexpected violence erupts in Chinatown during the festival of Tin Hau Don; Cullen confronts the Swede; and Durant involves Maggie in his latest scheme.

Cullen and Mei escort precious cargo through the California wilderness; Eva nurses Louise back to health.

Cullen and Durant meet with President Grant to discuss the future of the railroad; the Swede puts his plan against the Mormons in action.

The Swede's murderous rampage on the Hatch homestead results in a long overdue showdown with Cullen.

Cullen faces life-changing decisions in Utah as Truckee adapts to life without him.

Cullen's nitroglycerin experiment provides an explosive backdrop for the railroad life in Truckee. Durant's plan turns deadly.

Mickey's dirty business with Durant leaves him with blood on his hands. Meanwhile, Campbell's return to town complicates Louise's life.

Chang discovers Mei's secret and forces her to flee Truckee. Meanwhile, Cullen's search for her brings new realizations while exorcising old demons.

The race to finish the railroad comes down to inches, forcing all parties to contemplate the end of the line, and what the future holds for them.

The golden spike, government hearings and unpredictable actions mean new beginnings and endings for the survivors.