If you aren't already a convert to "Justified," you may wonder why a show about a U.S. marshal chasing a bunch of drug runners, moonshiners and murderers through the hills of Harlan County, Ky., winds up so consistently on lists of the top TV shows of the year.

Well, here's one reason: How often do you think the late British economist John Maynard Keynes gets name-checked in other action shows?

"Justified" returns for its fourth season on Tuesday, Jan. 8, showing no signs that its writers, producers and cast have decided to take it easy and the series' success for granted. "Justified" has pitted serenely cool Marshal Raylan Givens (Timothy Olyphant) against some magnificent villains in the past, like murderous matriarch Mags Bennett in season 2 and the icy Detroit sadist and Dixie mafia boss Robert Quarles last season, not to mention members of the Crowder family and Givens' own father, Arlo (Raymond J. Barry), through the entire series.

"Justified" was developed by Graham Yost based on the work of Elmore Leonard, who is the show's executive producer. The episodes are written and directed by a number of talented people, but consistently remain faithful to Leonard's luxurious writing style. And that's another reason "Justified" is so good: It is one of the TV's smartest and, yes, funniest shows, even if you don't know who Keynes was.

Characters have come and gone over the years, but Raylan's relationship with Boyd Crowder (Walton Goggins) remains central to the show's complex moral core. Old friends who find themselves on opposite sides of the law, Raylan and Boyd are like warring kings in a Shakespeare history play, each as brilliant and masterful as the other.

The new season finds Boyd worried about his drug empire when his customers start spending time - and money - at a traveling Pentecostal preacher's tent and Raylan trying to get to the bottom of a 30-year-old mystery when a couple of low-rent wire thieves smash a hole in Arlo's wall and discover an old Panamanian diplomatic pouch containing a driver's license for one Waldo Truth.

"Where's Waldo," the title of the second episode, is the question that may set the stage for the season. Not only do we want to know where and who Waldo is, but why his driver's license is in that old diplomatic pouch and what Arlo Givens knows about the whole thing.

The fourth season brings some new characters, including Constable Bob Sweeney (Patton Oswalt), who seems to have come from the Barney Fife School of Policin' Work. He only gets $2400 a year as the local constable, and has had to buy his own flashing red and blue lights, which he's affixed to the roof of his hatchback. Also new to the hills are Boyd's old military buddy, Colton Rhodes (Ron Eldard), who begins helping Boyd keep his drug business from collapsing, and Randall Kusik (Robert Baker), who shows up at Lindsey Salazar's (Jenn Lyon) bar and immediately tangles with Raylan.

Preacher Billy (Joe Mazzello) and his sister, Cassie (Lindsay Pulsipher), have set up their tent in Harlan County and are passing out fake million-dollar bills to advertise their arrival to the locals, who flock to the revival meetings to watch Billy handle poisonous snakes, promise them redemption from their wicked ways and a free pass to heaven.

Meanwhile, Ava (Joelle Carter) is busy trying to keep her empty-headed prostitute Ellen May (Abby May) in line, not only because she's an income source but also because Ellen May knows how Ava got rid of her former pimp. (This is serious stuff, but you'll fall off the Barcalounger laughing when Ellen May gets surprised by one of her frequent customers.)

The dialogue in the first two episodes of the new season crackles with brilliance. Even the most casual exchange between Raylan and Bob, or Boyd and the nefarious Wynn Duffy (Jere Burns) manages to be elaborately florid and completely credible at the same time. In fact, hearing just a bit of dialogue from "Justified" makes actors from other TV shows just sound like actors saying their lines.

Most tellingly, "Justified" has defied the tradition in TV that when one network has a great show that everyone is talking about, other networks tend to come up with imitations. That hasn't happened with "Justified," perhaps because its quality is incomparable.

"Justified" airs at 10 p.m. on FX.