In the eighth episode of Dexter 's third season, the fragile line between justice and murder blurs as Dexter Morgan brings Assistant District Attorney Miguel Prado into his dark world. The Mentorship of a Monster

While Dexter is meticulously clean and clinical, Miguel is euphoric, describing the experience as "fantastic". However, Miguel’s enthusiasm for the Code quickly wanes as he begins to see Dexter's rules as a hindrance rather than a necessity. Vanishing Acts and Dark Secrets

After Miguel expresses a desire to "get his hands dirty," Dexter decides to teach him —the strict set of rules his father, Harry, created to channel his homicidal urges toward other killers. Dexter views this as a way to control Miguel's volatility, but the ghost of Harry warns him that sharing the secret is a burden too heavy to bear.

As Dexter grapples with his new partner, Debra Morgan makes a breakthrough in the case.

They settle on Billy Fleeter , a former football player and debt enforcer who murders people to cover his gambling debts.

In a custom-prepared "kill room," Dexter lets Miguel take the lead. Miguel plunges the knife into Fleeter’s chest, claiming they represent "justice".