Dexter‘s Lumen was introduced as an intriguing new character in season 5 before making a surprising exit at the end of the season. Dexter deals with the titular Dexter Morgan, a vigilante-type serial killer who also works for the Miami Metro Police Department as a blood-spatter analyst. Over 8 seasons, Dexter followed a strict code given by his police officer father to only kill other murderers that deserve it, evade getting caught, and avoid emotional attachment with victims – a rule he broke through his intimate involvement with Lumen.
Julia Stiles signed on to Dexter in season 5 as Lumen, a role that earned her Emmy and Golden Globe nominations. The addition of Lumen also came in the first season after Dexter’s wife Rita was shockingly killed in the season 4 finale. In many ways, Lumen felt like a perfect character to fill that role in Dexter’s life. That made it all the more surprising when Lumen left the show so quickly, never to return again. While many fans of the show were sad to see her go, Lumen’s exit was always planned and made sense for her character.
Lumen is introduced in Dexter season 5’s first episode. When Dexter tracks a serial killer named Boyd Fowler to his home and kills him, he finds Lumen, one of Boyd’s would-be victims. After Dexter helps her to regain her strength and it becomes clear that she is not going to turn him into the police for the murder of Fowler that she witnessed, she reveals that Fowler was a small part of a bigger evil entity.
Lumen reveals that she was the victim of a group of men, eventually known as the Barrel Girl Gang, who capture, abuse, torture and kill women before disposing them in barrels. Though Lumen escaped the group, she suffered greatly at their hands and wanted revenge. When Dexter told her about his “dark passenger” and his code of killing, she became his sidekick in taking down the group of killers one by one. Throughout their work together, Dexter and Lumen fall for each other and begin a romantic relationship as well, with Dexter feeling a kinship he has rarely experienced.
Lumen felt like the most compatible of Dexter’s love interests and there was a mutual bond that formed between them. However, after killing the last of the Barrel Girl Gang members, Lumen decided that she could leave this life of violence behind now. Unfortunately, that meant having to leave Dexter as well. Dexter executive producer Sara Colleton told EW there was always a possibility for Lumen to return because she’s alive and her relationship ends amicably with Dexter.
However, the reasoning behind her leaving was that they wanted to show that someone can have their dark passenger for a time and abandon it to lead a relatively normal life. Lumen’s ending implies that Dexter can stop killing, but his darkness has obviously consumed him for much longer than Lumen’s. Lumen’s arc left Dexter with an optimistic future for himself and Harrison, considering Dexter can be seen for who he truly is and still be loved and Harrison doesn’t have to be doomed to a life of darkness after his trauma.
While Lumen never did appear on Dexter again after leaving at the end of season 5, the real missed opportunity for her return was in the sequel series Dexter: New Blood. Following the much-derided ending of Dexter in which he fakes his own death to live as a lumberjack in the woods, New Blood was seen as a way for the show to make up for that lackluster conclusion. The sequel series found Dexter living under a new name in a small community only for his dark passenger to become needed again.
However, the sequel series set up a perfect scenario for Lumen’s return. By the end of the series, Lumen was one of the few people who knew about Dexter’s dark passenger. It would make sense that, if he was going into hiding, he might try to reconnect with the only person who truly understood him. Lumen’s involvement in New Blood could have been very interesting with them living a quiet life together with her happy to leave the violence behind and him struggling to suppress those desires.
While the sequel series was seen as an improvement to Dexter‘s original ending, Lumen’s presence could have made it even better.