Showtime has picked up a second season of the dark serial killer dramedy "Dexter."

Production on the 12-episode second run will begin next spring for a 2007 premiere.

"Dexter is a home run for us, both critically and in popularity," raves Showtime Entertainment President Robert Greenblatt. "The show was launched at the height of all the broadcast networks' fall premieres yet instantly became our #1 rated show. People seem fascinated by the moral ambiguity of Dexter, as played by the gifted Michael C. Hall. This character and the world of this show are a welcome addition to our 'premium' line-up."

Hall plays Dexter Morgan, a Miami PD forensics expert and part-time serial killer prone to killing some of the city's worst criminals. The show's first season has followed the plot of Jeff Lindsay's novel "Darkly Dreaming Dexter" and co-stars Jennifer Carpenter, Julie Benz and James Remar, among others.

Because Showtime keeps its viewership figures close to the vest, it's hard to know how many people are watching "Dexter," but the Oct. 1 premiere drew 600,000-plus viewers, making it the channel's second most watched one-hour drama premiere behind "The L Word."

Meanwhile, despite teasing "Weeds" finale viewers with the promise of a third season, Showtime is still reportedly finalizing a formal deal, though an announcement is expected soon.