Cullen is in California with the Central Pacific Railroad, and must deal with the new workers.
Cullen enlists new workers to help him move a locomotive on a sled.
Cullen must deal with the violence in Chinatown, caused by disgruntled workers.
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 take a dangerous journey through the California wilderness, escorting precious cargo. Meanwhile, Eva nurses Louise back to health.
Cullen and Durant reunite in Salt Lake City to meet with President Grant about the future of the railroad. Meanwhile, Swede enacts his plan against the Mormons.
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. Meanwhile, Durant's lies compromise his new partner.
Cullen's nitroglycerin experiment provides an explosive backdrop for the railroad life in Truckee. Meanwhile, 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.
