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