"Dexter's" problems are proving a boon for Showtime.

The serial-killer drama unfurled its fifth season Sunday with its best-ever season-opener ratings. A total of 1.8 million viewers tuned in, according to the Nielsen Co. Another 575,000 watched a rebroadcast at 11 p.m., for a same-night total of 2.3 million.

That was a bit below the record-breaking Season 4 finale (2.6 million), in which Dexter (Michael C. Hall) found his wife murdered. But it was Showtime's best season premiere in 15 years and the network's most-watched program so far this year.

-- Scott Collins

Twitter: @scottcollinsLAT

Photo: Michael C. Hall in "Dexter." Credit: Peter Lovino / Showtime