Dexter and Jordan Chase are seen here on dueling treadmills. They each went to learn more about the other.
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Dexter doesn't just deal with Rita's death on season five. He deals with a new character by the name of Lumen.
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Dexter Season 5 Episode 9 Quotes

Lumen: Share something with her - what you did when you were her age.
Dexter: I killed the neighbor's dog.
Lumen: Well, don't tell her that.

Dexter (thinking to himself): Jordan is one tough nut to crack.
Jordan (out loud): You're one tough nut to crack; you know that, Dexter?
Dexter (still thinking): I wish he'd stop doing that.