<P> Events lead to Debra dating a prosthetics technician named Rudy Cooper, who is also interested in befriending Dexter . Dexter later finds out that a recently deceased man named Joe Driscoll was his biological father, meaning that the man didn't die when he was a child and that Harry lied to him . While he's in the midst of discovering this, Dexter is introduced to Rudy, who says he has been waiting for a long time for them to meet, and the two begin a friendship, although it becomes clear to the audience that Rudy is responsible for the death of Dexter's biological father . Debra is confused that at times Rudy seems more interested in Dexter than in her . </P> <P> Arriving at a scene arranged by the Ice Truck Killer, a hotel room covered in blood, Dexter suffers a panic attack and realizes that he is regaining his repressed memories . Investigating his past, he learns that Harry found him at the scene of a vicious murder when he was a child . Eventually, he remembers that he and his mother, a woman named Laura Moser, were in a shipping container, imprisoned by criminals . These criminals then killed Laura and chopped her up with chainsaws in front of Dexter, then left him locked in the container, sitting in his mother's blood . It was not until two days later that Harry and the police found Dexter and his dismembered mother . After taking Dexter in, Harry arranged for the report on his discovery and the circumstances of his mother Laura Moser's death to be destroyed . </P> <P> It is revealed to the audience that Rudy Cooper is actually the Ice Truck Killer . After attempting to kill Det . Batista, who was closing in on him, Rudy proposes marriage to Debra . But this is a ruse to kidnap her and use her as bait for Dexter . Rudy's clues lead Dexter back to his childhood home, where Rudy is holding Debra . Dexter recalls now that he had an older brother who was also in the container when their mother Laura was murdered . Rudy Cooper is actually his older brother, Brian Moser, who was not adopted and spent much of his life in mental institutions . Like Dexter, he is a serial killer but not bound by a moral code . Rudy reveals that he has been searching for Dexter for years and was happy to realize that his younger brother was also a killer . For months now, he has been leading Dexter to him and helping his younger brother recover the memories of their shared childhood trauma . Rudy then reveals a room covered in plastic, where an unconscious Debra is naked and taped to a table . Rudy has arranged the room to be just as Dexter prefers for his own kills, and says that they will kill Debra together to cement their bond as brothers . Dexter says he won't kill Debra and Brian protests that his brother "can't be a killer AND a hero ." Dexter saves Debra from Brian just as she wakes up and Brian escapes as the police arrive . </P> <P> Doakes suspects that Dexter knows more than he's sharing and may have been helping "Rudy Cooper," but Debra insists that Dexter saved her from the Ice Truck Killer . Rudy's biological connection to Dexter is kept secret . Brian Moser makes another attempt on Debra's life, but falls into a trap set up by Dexter . Determined to keep Debra safe, Dexter kills Brian and arranges the scene so the police are convinced that the Ice Truck Killer committed suicide . This time, Dexter does not keep a blood slide trophy of the kill . The season ends with Rita wondering if Dexter did indeed set - up her husband to be imprisoned again, while Dexter realizes that Doakes, now convinced the blood spatter specialist is hiding something, is monitoring him closely . </P>

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