[1] The episode's frame story picks up from "Sins of the Father", the finale of Dexter: New Blood, where after being shot by his son Harrison, Dexter Morgan (Michael C. Hall) is taken by the police to a hospital and revived by doctors after flatlining, where-upon his "life flashes before [his] eyes" to when he first began working as a forensic blood spatter analyst at the Miami Metro Police Department, the series exploring the younger Dexter (Patrick Gibson) and his inner conflicts, wherein he began his days as a serial killer.
In December 2021, after being shot by his son,[a] a critically wounded but still alive Dexter Morgan (Michael C. Hall) is taken by the police to a hospital.
Upon investigating, Dexter concludes that Harry's caretaker, Nurse Mary (Tanya Clarke), is poisoning him with injections, which she has done to other patients.
[b] He checks her office and finds that she keeps the obituary papers of her victims as trophies, and confirms that her injections contain high levels of potassium nitrate.
When he arrives home in the morning, Dexter meets Harry's co-workers from Miami Metro; Captain Aaron Spencer (Patrick Dempsey), CSI Chief Tanya Martin (Sarah Michelle Gellar), forensics specialist Vince Masuka (Alex Shimizu), Detective Angel Batista (James Martinez), and Detective Bobby Watt (Reno Wilson).
Phillips explained that the fandom's negative reception to the episode made him consider changing it, and Michael C. Hall convinced him that he could continue playing Dexter if he found a way for the character to survive.
You can't plan for everything, but I think all of those elements and aspects certainly led to who Harry ends up becoming and expressing unconditional love for Dexter.
Club gave the episode a "C–" and wrote, "To be fair to this awkward premiere, the final scene of “And In The Beginning…” feels like the real start to Dexter: Original Sin.
Dexter Morgan arrives to his first day on the job at Miami PD, ready to help solve cases in a way that satisfies his vengeful inner psychopath.
And Gibson comes to life in this scene a bit, as if he's finally becoming the Dexter we know after saving both his father and sister, taking a murderer off the streets, and finding the job of his dreams.
"[7] Louis Peitzman of Vulture gave the episode a 4 star rating out of 5 and wrote, "As far as shameless brand extensions go, this series feels mostly harmless, and it's off to a promising enough start that we can overlook how desperately Showtime is determined to squeeze the life out of this franchise.
In an era of endless IP, Dexter: Original Sin is at least entertaining, and that's more than can be said for countless other recent cash grabs.
"[9] Mads Misasi of Telltale TV gave the episode a perfect 5 star rating out of 5 and wrote, "When a character has already been established, continuing the franchise with a sequel or a prequel becomes daunting.
"[10] Greg MacArthur of Screen Rant wrote, "A two-episode premiere of Dexter: Original Sin might have been the way to go for Paramount.
If Dexter: Original Sin gives us more of this killer Gibson-Hall combo, it could easily salvage its stumbling start.