"dexter" Popping Cherry(2006) -

A younger, less refined Dexter kills Mary by stabbing her after tying her to a table with plastic wrap, marking the birth of his signature ritual. Cast and Crew

Parallel to the main investigation, Dexter stalks , a teenager recently released from prison after killing a boy years earlier. Dexter believes Jeremy will kill again and nearly catches him in the act before intervening. Meanwhile, Rita faces harassment from a drug dealer associate of her imprisoned husband, Paul, who confiscates her car as payment for Paul's debts. The Flashback: Dexter's First Kill

The episode's title refers to Dexter "popping his cherry" as a serial killer. Through flashbacks, we see:

In the present day, the leaves another victim, a woman named Cherry, dismembered and displayed at a Miami hockey rink. While Lieutenant Maria LaGuerta focuses the investigation on Tony Tucci, a missing security guard, Debra and Dexter suspect he is actually another victim being framed by the real killer.

Harry discovers Mary is administering overdoses to her patients and gives Dexter "permission" to make her his first target, provided he follows the "Code".