After doing almost exclusively Westerns (Gunsmoke, How The West Was Won), James Arness' final series was a contemporary crime drama, McClain's Law, which aired on NBC in 1981. Amazingly, none of the critics thought to refer to this as Arness essentially reprising his signature role as Marshal Matt Dillon (Gunsmoke) in a late-20th century setting. Maybe it's for the best that they didn't, since the show lasted just six months.
So why did McClain fail? Hard to say, really. NBC had the show coupled at one point with Angie Dickinson's comeback vehicle, Cassie & Co., on Fridays, but at the time, NBC was struggling to find a hit drama other than Little House on the Prairie, and while Hill Street Blues was part of the same freshman class as McClain, viewers found that more to their liking, perhaps because it didn't have a familiar face headlining the show.
Following is a clip from the series' finale, "The Last Hero", with guest star Gregory Sierra (ex-Sanford & Son, Barney Miller, Soap) as a Vietnam veteran in need of treatment for his kidneys, and his friends are holding McClain hostage.