Michelle Dockery’s new role is a far cry from “Downton Abbey.” Within the first few minutes of TNT’s “Good Behavior” pilot, the former Lady Mary is scrubbing brown slime out of a clogged toilet in a backwoods diner. It’s understandable, this need to go as far as you can in the opposite of the role that defined you. But does her new outing succeed?

First, the good: The woman can rock an American accent. It’s got a slight tinge of the unplaceable — think Hugh Laurie, and Benedict Cumberbatch’s Dr. Strange — but it’s still believable. What’s more, she can segue between slight-twang (her character hails from somewhere in the south) to full-on drawl. She seems pretty comfortable playing an unraveling American woman with a drug habit. It’s an impressive display of range from someone who spent five years as one of TV’s most iconic aristocratic Brits.

Dockery’s character, Letty Raines, is a mess of a woman who has a prison record and a young son from whom she’s blocked by a restraining order, who nurses several bad habits including meth, and makes most of her money via petty theft and grifting. We see her in an array of wigs as she enacts one con after another, bringing the loot back to her dingy motel room, where she hilariously listens to self-improvement tapes while she’s trying on stolen clothes (or, at one point, smoking meth out of a lightbulb, as a voice intones, “I am centered and well-balanced. I can feel how beautiful I am.”)

I have to admit to some wig fatigue here, though I know legions of “The Americans” fans out there will beg to differ. Are we really still so fascinated by the sight of a beautiful actress sashaying around looking like a slightly different beautiful woman? Are there not more subtle ways to connote taking on a different persona? Didn’t “Alias” sort of own the whole wig thing? But I digress.

In the pilot, directed by veteran TV helmer Charlotte Sieling, Letty gets mixed up with an assassin named Javier (Juan Diego Botto) who’s contracted by a man to kill his wife. Caught mid-robbing Javier’s room, she hides in the closet and overhears the plan, then finds herself crippled with a surprising twinge of morality as she debates whether or not to do anything about what she’s heard; she ends up seducing Javier to find out more information. The action that ensues is rather dime-a-dozen. Botto is handsome but, so far, otherwise unremarkable as a sparring partner for Letty.

The moral arc of “Good Behavior” is flexible, to say the least. Our heroine is, obviously, not a paragon of what the title advertises. There is a development toward the end of the pilot that, without spoiling it, rather casually squanders the life of someone we’d come to know a bit about.

But my main complaint is actually that the show doesn’t really allow us to get to know Letty’s ice-cold grifter side before assuring us that she’s actually a decent person deep down where it counts. The best con-woman dramas don’t get to that part till much later on (if ever) — I’m thinking nostalgically here about Linda Fiorentino in the great “The Last Seduction” – and allow you a good run of just seeing them enjoying being bad. Heck, if you’re going to sardonically call your show “Good Behavior,” well, why not let your main character wallow in the other kind?

Dockery is clearly having a blast playing the part, and this being only the first episode, there’s a good chance her character will bloom into some complexity over the next episodes (this one and a second will run together on November 15). We can always hope the “good” Letty is just running a long con on the viewer.