Seth Bullock was a sheriff in Montana, but he had his fill of hangings and decided to retire. Hearing of the goldrush in Deadwood, but not liking to speculate by buying a claim, he partnered with his friend Sol Star to start a hardware business there. He planned on taking things easy, but not long after he arrived in town Wild Bill Hickock showed up, and the two became friends while investigating the slaughter of an immigrant family. Together they shot down one of the men responsible, and Bullock was fast enough that Wild Bill wondered whose bullet had taken him down.
Bullock attracted the admiration of Bill's friend Charlie Utter, who despite Seth's temper saw that Bill could learn a lot about how to deal with people and be a regular human being from Bullock. Utter and Bullock remained friends after Bill's death.
A firm believer in justice, it was Bullock who tracked down Jack McCall after a court in Deadwood acquitted him of Wild Bill's murder, and he also took on the task of looking after Alma Garret's gold claim at Bill's request. He fell for Mrs. Garret, but found it difficult to deal with his feelings as he had married his brother's widow in order to make sure she and his nephew were looked after. Though it is a loveless marriage, he feels strongly responsible for his wife and adoptive son.
No lover of the trappings of religion - he has no time for the preacher's sermons - Bullock nevertheless sees that every man he hangs gets his last prayer, and every man he kills gets put in the earth (or the heathen equivalent) in proper fashion.