The First episode of Season 3 deals with the aftermath of Dexter having saved his long-time girlfriend's children from a fire, as well as his sisters interest in a new guy, as well the fact that Dexter's girlfriend is pregnant with what could be Dexter's kid. The entire cast from Season 2 reappears with exception of Sgt Dokes, who was killed off towards the end of the second season.
The plot revolves around the addition of a new lawyer/seargent member, who's son Dexter accidentally kills in a case of misunderstanding. Seargent Santiago, in guilt of Doke's death, feels as if Dokes was murdered and sets out to clear Doke's name and find the real killer - who Dokes alluded to as Dexter. Also Dexter's sister is slowly starting to suspect and will probably soon find out about Dexter's secret life this season. In my attempt to not reveal anything that would ruin the episode, I've omitted certain details.
There's quite a few sex scenes in this Dexter episode. Also for "some" reason this isn't making much headlines or discussion:
Watch Dexter Season 3 Episode 1 - Our Father (MS)