"When Chloe and Lucifer's investigation into the murder of a diamond thief points to one of Ella's brothers as the main suspect, Ella is driven to prove her brother's innocence and recruits an unlikely ally. Meanwhile, Linda is upset when Charlotte comes to her for help and Detective Pierce hashes out his issues with Amenadiel."
Lucifer, realizing that he understands nothing about Cain's mark, decides to ask Amenadiel for help, but he refuses. Ella's older brother, Jay Lopez, disappears after a man he was meeting with is murdered. Chloe asks Ella to recuse herself from the investigation, but she and Maze go off to find him anyway. Charlotte is turned down by Linda when she asks for a consultation, as she still fears her. The victim is tied to a jewelry store heist, and Lucifer and Chloe check with the owner, who reveals that the "robbery" was actually insurance fraud. Pierce tracks down Amenadiel, who he knows gave him the mark, and assaults him in anger. Chloe and Dan confirm that Jay was, in fact, hired to "clean" the stolen diamonds. Jay flees, and goes after the real killer, the store's investigator, but gets captured. Pierce points out that he and Amenadiel both tried to kill their brothers, but that Amenadiel's failure makes him worse. Maze eliminates the killer and saves Jay. Linda decides to treat Charlotte. Lucifer catches Jay stealing the diamonds, and vows to punish him if he ever commits a crime again. Amenadiel decides that he will do whatever it takes to protect his brother from Pierce.