The episode centers on Cullen Bohannon (Anson Mount) fighting for his life as he answers for Johnson's death.

Meanwhile, Lily Bell (Dominique McElligott) struggles to survive in the wilderness, Thomas Durant (Colm Meaney) attempts to spin tragedy for political gain, and Joseph Black Moon (Eddie Spears) tracks down the Cheyenne braves responsible for a massacre only to find one of them is his own brother (Gerald Auger).

Cullen Bohannon (Anson Mount) gets introduced to a man known as "The Swede", Durant's head of security at Hell on Wheels.

Joseph Black Moon (Eddie Spears) finds the Cheyenne braves responsible for the massacre - one of which is his brother, Pawnee Killer (Gerald Auger).

Durant asks him to offer a $100 reward for Lily's return, adding his orders to not say a word about the missing maps.

When Bohannon goes into Johnson's former headquarters, he finds in his jacket a stitching that belonged to his deceased wife and ponders getting revenge on the last man that killed her.

Adam Raymond of New York Magazine stated the episode "spent the majority swinging more hammers in an attempt to get to a place that’ll allow this train to finally get out of the station.

"[2] TV Fanatic's Sean McKenna approved of the episode: "Thankfully, 'Immoral Mathematics' managed to focus itself on one central storyline and scatter a few smaller ones throughout.