NCIS, the TV's most-watched drama series, has been renewed for a 19th season with Mark Harmon returning as Leroy Jethro Gibbs, despite reports of his retirement earlier this year. The actor negotiated to return after CBS threatened to cancel the show if he left. It is unclear whether he will appear in all episodes or just some. NCIS attracts an average of 12 million viewers per episode, but it is also the most expensive show to produce on CBS network. Fans will be relieved to hear about Harmon's return after losing Paulette Perrette's character in the 15th season and Michael Weatherly's character in the 13th season.