<P> "Return to Sender" is the sixth episode of the first season of the American television drama series Dexter, which first aired on November 5, 2006 on Showtime in the United States . The episode was written by Timothy Schlattmann and was directed by Tony Goldwyn . In the episode, Dexter Morgan (Michael C. Hall) investigates a murder scene where one of his own victims has returned after he disposed of the body . Meanwhile, his girlfriend Rita Bennett (Julie Benz) tries to prevent her husband Paul from attending their daughter's birthday party, and Lt. María LaGuerta (Lauren Vélez) considers adopting a young witness of the murder whom she finds at the crime scene . </P> <P> Though set in Miami, Florida, the episode was filmed at various locations in and around Los Angeles, California including a salvage yard, a field by Tujunga Wash and a waterfront house on Hibiscus Island . Goldwyn, who Erik King said was "a joy to work with", allowed actor C.S. Lee to improvise and David Zayas to memorize his Spanish lines in English and translate them mentally during each take . "Return to Sender" received generally positive reviews from critics . </P> <P> While eating breakfast at Rita's house, Dexter is called to a crime scene, only to discover that it is the same salvage yard where he committed a double murder the previous night . He finds Valerie Castillo's (Valerie Dillman) body lying in the Airstream trailer where he killed her and her husband Jorge (José Zúñiga), despite having thrown the corpses into the ocean . He deduces that the "Ice Truck Killer"--a serial killer with whom Dexter has a personal connection--dived underwater to retrieve the woman's body and plant it in the trailer . In the yard, LaGuerta, Sgt . James Doakes (Erik King) and Dexter's sister Debra (Jennifer Carpenter) discover a young Cuban boy, Oscar (Cesar Flores), hiding in the trunk of a car who claims to have seen somebody take Valerie into the trailer . He begins to fear discovery, and experiences his first nightmare: Debra is a serial killer with an identical modus operandi to Dexter . As the investigation proceeds, he attempts to shoot down each of his colleagues' leads on the case . When Debra asks him to read through her report on the killer, profiling a man sharing many of Dexter's characteristics, he second - guesses her theory and she is hurt . Worried about coming under suspicion, he throws all of his knives overboard from his boat, but while looking at the blood drops from his victims, he notices that Valerie's slide has a happy face etched into the blood . He realizes that this is a hint from the Ice Truck Killer, and plants Jorge's fingerprints and a dry drop of Valerie's blood onto a knife, which he hides in a car at the salvage yard . He convinces Doakes to organize another search of the yard, where an officer (Denver Dowridge) finds the knife . After successfully framing Jorge for Valerie's murder, Dexter discovers that Oscar's description of the man who "saved" him from Valerie is in fact Jesus Christ . </P> <P> Meanwhile, Rita dissuades her abusive husband Paul from attending their daughter Astor's (Christina Robinson) birthday party after he is released early from prison . Doakes takes Debra to dinner with his mother (Vernee Watson - Johnson) and sisters, while LaGuerta bonds with Oscar and considers adopting him until his uncle (Gabriel Salvador) arrives to take him home . </P>

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