According to Waverly Earp, Robert Malick is "a hellfire revivalist minister known to rail against women, demand they repent". Wyatt Earp hung Malick for murdering his wife, girlfriend, and hookers. However, the Wynonna Earp website states that Malick was killed in 1881 in a shootout with Wyatt.
When a citizen of Purgatory is murdered with the phrase "Repent Sinners" written on their mirror, Waverly assumes that it was Malick who did it, due to his religious background and hatred for women. Wynonna Earp and Xavier Dolls go to Bobo's Trailer Park to question Malick. Despite him being a generally unpleasant person (he calls Wynonna as well as women in general whores several times), the pair quickly realize it wasn't him when they discover both of his legs had been amputated. Malick warns Wynonna that the real killer, August Hamilton, will eventually go after her.