On the episode "Road Kill," Dexter never got a chance to use this kill room. He actually ended up saving Trinity's life instead.
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What is Trinity up to? He takes Dexter along for a road trip on the episode "Road Kill."
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Dexter Season 1 Quotes

[narrated, in reference to Doakes] My devil danced with his demon and the fiddler's tune is far from over.

Dexter Morgan

The only real question I have is why in a building full of cops, all supposedly with a keen insight to the human soul, is Doakes the only one who gets the creep from me.

Dexter Morgan