Summary

• Key characters like Deb and Brian discovered Dexter's dark passenger, leading to dramatic confrontations and secrets revealed.
• Dexter's adoptive father, Harry, gave him a moral code for killing, but ultimately couldn't handle the monster he created.
• Other characters like Isaak, Lumen, and Vogel played significant roles in Dexter's journey as a vigilante serial killer.

Although Dexter's killer protagonist was always careful not to get caught, there were a number of key characters who find out about Dexter Morgan’s dark passenger over the course of the series. Dexter documents the life of Dexter Morgan, a vigilante serial killer who also happens to be the blood-spatter analyst for the Miami Metro Police Department. Dexter operates his serial killing unconventionally, sticking to a strict code where he can only kill those who deserve it — confirmed murderers who have evaded the justice system.

While trying to appease his dark passenger’s need for blood, Dexter has to carefully avoid getting caught while on the hunt and after he kills. His most important rule while serial killing is to not be caught, which means not letting anyone know his real identity or acting in a way those around him find suspicious. Aside from his many victims that obviously knew Dexter was a dangerous killer in their final moments, only a select few established characters found out about Dexter's dark passenger. From loved ones to adversaries to new allies, these characters discover his darkest secret.

Harry Morgan

Played By James Remar

After finding him in a pool of his mother’s blood in a shipping container, police officer Harry Morgan adopted Dexter as his own son. As Dexter grew older, Harry noticed abnormalities in his son, especially his interest in blood, withdrawn demeanor, and need to kill animals. Realizing Dexter would either need to be institutionalized or likely end up in prison for homicide, Harry decided to use Dexter’s killer affinity for good.

Once Dexter killed his first human being (an evil nurse), Harry gave Dexter the “Code of Harry,” which outlined Dexter’s rules for killing.

Once Dexter killed his first human being (an evil nurse), Harry gave Dexter the “Code of Harry,” which outlined Dexter’s rules for killing, including not getting caught and only killing murderers who escape justice. During this time, Harry had been seeing a therapist who helped “create” Dexter into the vigilante he was, before it all became too heavy of a burden.

After physically seeing Dexter murder and chop up one of his victims, Harry became physically sick. Knowing what he created in Dexter and what he had seen, Harry Morgan ended up committing suicide.

Debra Morgan

Played By Jennifer Carpenter

In one of the most memorable moments of his secret being revealed, Dexter's adoptive sister Deb learned Dexter and Harry had hidden his serial killing from her all her life. Even as an adult, when Debra was Dexter’s closest connection, he could never tell her because he didn’t want to burden her with the knowledge and figured that, as a cop, she would feel the need to turn him in. Finally, in Dexter’s season 6 finale, Debra happened upon Dexter murdering The Doomsday Killer in his ritualistic fashion at the church.

At first, Deb didn’t know Dexter was a serial killer and only tried to help cover up his apparent one-time murder.

At first, Deb didn’t know Dexter was a serial killer and only tried to help cover up his apparent one-time murder. As season 7 progressed, Debra found out that Dexter was a methodical serial killer and that their father helped guide him, causing her to be physically ill. Because Deb loves Dexter so much, she still helped hide his identity, even when it led her to make the life-altering decision of killing Maria LaGuerta.

The guilt of committing a murder of her own ate away at Deb until she eventually reconciled with Dexter. After going into a coma due to a gunshot wound, Dexter euthanized her in an act of love.

Brian Moser (Ice Truck Killer)

Played By Christian Camargo

Aside from Harry, Brian Moser was the first character who revealed he knew Dexter Morgan was a serial killer. He was first introduced as Dexter season 1’s villain, the Ice Truck Killer, under a different alias before explaining he’s actually Dexter’s biological older brother. Brian was also in the shipping container when their mother was murdered, but Harry only adopted Dexter.

Dexter decided to put him down, though Brian’s legacy haunted him throughout the series.

He kept tabs on Dexter and discovered his younger brother had also developed an affinity for blood and killing, leading Brian to track down Dexter and taunt him with crime scenes and images of their traumatic past. After discovering how dangerous Brian was and that he nearly killed Dexter's sister Deb, Dexter decided to put him down, though Brian’s legacy haunted him throughout the series.

James Doakes

Played By Erik King

Dexter explains that from the beginning of Dexter Morgan and Sergeant James Doakes working together, the latter always had an overt suspicion of the former — mostly just thinking he was weird for being so into blood. Once Dexter’s underwater graveyard of victims is discovered in season 2, the entire police department must search for the Bay Harbor Butcher without realizing he’s working alongside them. While many in the department shoot down such suspicions, Doakes stalks Dexter as he truly believes him to be the killer.

Since Doakes had the murder weapons and Dexter’s blood slide box, the department wrongly pinned him as the Bay Harbor Butcher.

After tracking Dexter to one of his kills, he becomes Dexter’s hostage in a remote cabin. After a few episodes of Dexter keeping Doakes in a cage and revealing his serial killing, Dexter’s girlfriend Lila shows up to kill Doakes herself. Since Doakes had the murder weapons and Dexter’s blood slide box, the department wrongly pinned him as the Bay Harbor Butcher.

Lila West

Played By Jaime Murray

Lila is introduced in Dexter season 2 as Dexter’s sponsor at Narcotics Anonymous, who invented the phrase “dark passenger” for him. Though he is with Rita, Dexter felt a connection with Lila and the two engaged in an affair. Dexter never actually told Lila about his penchant for serial killing. She found out when she tracked Dexter’s GPS and finds Doakes. Doakes then informed Lila that Dexter is the Bay Harbor Butcher, but the warning had the opposite effect than intended.

In addition to killing Doakes, Lila also tried to kill Rita and her kids to further cement her and Dexter's love.

Instead of helping Doakes escape so he could bring Dexter to justice, she decides to show her love for Dexter by protecting him. She set the cabin afire with Doakes inside. In addition to killing Doakes, Lila also tried to kill Rita and her kids to further cement her and Dexter's love. This was enough to make her Dexter's next target, as he tracked her down while she was hiding out in Paris and killed her.

Miguel Prado

Played By Jimmy Smits

Miguel Prado was introduced in Dexter season 3 as the D.A. looking for whoever killed his young brother, who just happened to be Dexter Morgan. While trying to hide his own identity and accidental kill, Dexter went to kill Freebo, suspected of killing Miguel’s brother. However, Miguel catches him with the murder weapon in his hands. Miguel believes that Dexter killed Freebo in self-defense, and they even become best friends, spending much time together outside the investigation.

In addition to killing Doakes, Lila also tried to kill Rita and her kids to further cement her and Dexter's love.

As they grew closer, Miguel found out Dexter had avenged other deaths, eventually revealing to Miguel that he was a serial killer. Miguel becomes Dexter's sidekick where they find victims together. However, Miguel eventually started using these new skills to kill his personal enemies who are not criminals, including Ellen Wolf, and attempted to kill LaGuerta. Dexter recognized the monster he created with Miguel and killed him as well.

Lumen Pierce

Played By Julia Stiles

Introduced in Dexter season 5, Lumen Pierce was found by Dexter as a hostage in the home of one of his murderous victims. When Dexter saw Lumen, she knew that he had just killed Boyd Fowler. However, he knew that he had to rescue her. Dexter and Lumen then team up to hunt down her other torturers in the Barrel Girl Gang. Along the way, their dark mission led them to develop a romantic relationship.

Once she had her revenge and ensured other women wouldn't fall victim to these men, Lumen realized that she didn't want to remain in a life of violence

Lumen was the first person to whom Dexter could truly disclose his life’s story, telling her that he had killed habitually and that he lived life as a serial killer. She stayed with him throughout the rest of the season until they killed every member of the Barrel Girl Gang. However, once she had her revenge and ensured other women wouldn't fall victim to these men, Lumen realized that she didn't want to remain in a life of violence and that meant she had to leave Dexter.

Maria LaGuerta

Played By Lauren Velez

Although for most of the series Maria LaGuerta was adamantly against putting Dexter under suspicion of killing, she concluded that he was the Bay Harbor Butcher herself in season 7 shortly after Debra also learned the truth about Dexter in season 6. Though everyone else believed that James Doakes was the killer, LaGuerta always maintained the innocence of her late friend and that caused her to dig deeper, eventually leading her to suspect Dexter.

LaGuerta then stalked Dexter and tried to set him up by catching him at kills, finally finding him in the middle of killing Hector Estrada at the shipping yard.

LaGuerta then stalked Dexter and tried to set him up by catching him at kills, finally finding him in the middle of killing Hector Estrada at the shipping yard. She confronted Dexter before Deb showed up. Deb had to choose between protecting her brother or killing her innocent boss and reluctantly chose the latter. With LeGuerta's death, she ensured Dexter was safe.

Hannah McKay

Played By Yvonne Strahovski

Hannah McKay was introduced in Dexter season 7 as the accomplice to a serial killer when she was younger. Dexter then discovers that Hannah has still been killing, deciding to put her on his table. The moment Hannah discovers Dexter's dark passenger is when she wakes up on his table, though instead of killing her, they end up becoming intimate. It is another moment of Dexter finding kinship in somebody who understands his dark side.

Dexter tells her he kills “bad people,” which is a description they both agree she fits.

Dexter tells her he kills “bad people,” which is a description they both agree she fits. Dexter refuses to kill Hannah, even when Deb asks him to, because they are in a romantic relationship. Over the next two seasons, Hannah remains Dexter’s on-and-off girlfriend until he fakes his own death and flees, leaving his son Harrison Morgan in her care in Dexter's season 8 finale.

Isaak Sirko

Played By Ray Stevenson

For much of Dexter season 7, the antagonists are a group of Ukrainian mobsters in the Koshka Brotherhood who come to America to find the person who murdered one of their associates, Viktor. Isaak was the leader of his team, and had a personal vendetta over the murder. Isaak proved to be very efficient at his job and quickly found that Dexter was the man they were after.

As someone who acted based on love and not reason, Isaak came to an understanding with Dexter.

However, Isaak learned that Dexter killing Viktor wasn’t out of vengeance, but was simply a case of Victor's criminal world intersecting with Dexter's existence as a serial killer. As someone who acted based on love and not reason, Isaak came to an understanding with Dexter. The two form an amusing friendship of sorts, with Isaak baffled by Dexter's cluelessness about love and romance. Dexter and Isaak agree to kill Isaak’s mafia acquaintances, though Isaak was fatally wounded by George before Dexter could get to him.

Dr. Evelyn Vogel

Played By Charlotte Rampling

In season 8 of Dexter, a new psychologist, Dr. Evelyn Vogel, came to Miami to help with The Brain Surgeon case. She revealed to Dexter that she knew him even if he didn’t know her, because Harry had come to see her in therapy once discovering Dexter had psychopathic tendencies as a child. Dr. Vogel tells Dexter that she was the one who helped Harry design the “Code of Harry” that Dexter lived by, where she had originally suggested using Dexter’s blood affinity for good.

She called herself Dexter’s “spiritual mother” as she helped turn him into the moral serial killer he became.

She called herself Dexter’s “spiritual mother” as she helped turn him into the moral serial killer he became. Evelyn also revealed that she is the mother of another serial killer who now goes by the name of Oliver Saxon. As Dexter hunted Saxon, he was able to convince Evelyn that her son could not he reformed. However, before Dexter can catch the killer, Saxon murders his own mother.

Zach Hamilton

Played By Sam Underwood

Zach was another young psychopathic patient of Dr. Vogel. Because of her own son's crimes, Vogel made it her mission to help young people with killer tendencies, hoping she could guide them down a better path. With Zach, she hoped to achieve that by assigning him to Dexter to teach him about the code he used as a killer.

Though Zach has a darkness in him, he is shown to have taken to the code well and sees it as a possible way of controlling that darkness.

Dexter openly discusses his own Dark Passenger with Zach and develops a mentor relationship with the young man. Though Zach has a darkness in him, he is shown to have taken to the code well and sees it as a possible way of controlling that darkness. However, Zach never got the chance to explore this new life as he was murdered by the serial killer Oliver Saxon aka The Brain Surgeon toward the end of Dexter season 8.

Angela Bishop

Played by Julia Jones

When the audience is introduced to Dexter in Dexter: New Blood, he is living a new life under a new name and even has a new girlfriend. Angela Bishop is the Chief of Police in the small community of Iron Lake. While she might not be a big city cop, she proves herself one of the most intelligent investigators in the series and that leads to her uncovering the truth about Dexter.

She is able to piece together the evidence and conclude that he is the real Bay Harbor Butcher.

After meeting with Miami detective Angel Batista, Angela is able to make the connection that the man she thinks is Jim Lindsay is actually Dexter Morgan. Even more impressive, she is able to piece together the evidence and conclude that he is the real Bay Harbor Butcher. Angela manages to accomplish what no other cop on the show did and arrests Dexter for being a serial killer, even though he later escapes.

Harrison Morgan

Played by Jack Alcott

Harrison Morgan appeared on Dexter at various ages, but it is when he reappears as a young man in Dexter: New Blood that he gets to know his father's dark secret. After tracking down his father, Morgan is saved by Dexter from another killer and sees him take the man's life. Eventually, Harrison begins joining his father on some of these kills and learns that he has killed hundreds of people.

Harrison sees the code Dexter lives by and seems to accept it, although he is clearly not comfortable with it.

Harrison sees the code Dexter lives by and seems to accept it, although he is clearly not comfortable with it. However, when Dexter kills an innocent man to escape prison, Morgan begins to see his father simply as a killer and suggests that he is the reason his mother Rita was killed. In the end, Harrison shoots Dexter to prevent any more bloodshed and Angela covers his tracks.