Farscape/Recap/S04 E15 Mental As Anything

Season 4, Episode 15:

Mental as Anything
While the women are shopping for supplies on an asteroid outpost, the men of Moya's crew visit a man named Katoya who can teach them forms of mental conditioning. Scorpius believes it will help Crichton to resist the Scarran heat probe should he ever encounter it, but Crichton is more concerned with finding out if Katoya knows anything about the creature that attacked his family. During the training, D'Argo discovers that someone else has arrived to learn from Katoya: Macton, the brother and murderer of Lo'Laan, D'Argo's wife. D'Argo is determined to take revenge, but Macton throws doubt onto D'Argo's strongest convictions about what happened on the night Lo'Laan died.

As D'Argo's Luxan hyper-rage and Macton's love for his sister are examined, the truth about what happened comes to light: when Macton threatened to get rid of D'Argo, Lo'Laan tried to stab her brother to save her husband. Macton instinctually defended himself and killed Lo'Laan, then beat her corpse to make it look like D'Argo did it in a fit of Luxan hyper-rage. Macton is left in a coma, forced to relive the memories of killing his sister, while the men of Moya leave. Crichton and Scorpius discover that the creature they encountered on Earth was most likely reporting to Grayza, and the Peacekeepers now know the location of Earth.