BUG

At the Barrow Street Theatre, 27 Barrow St. Telecharge, (212) 239-6200.

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SHANNON Cochran makes a very sexy desperado.

At the start of Tracy Letts’ “Bug,” Cochran, as the lonely Agnes, leans against an Oklahoma City motel door, puffing dreamily on a cigarette. But she has no idea what’s in store for her.

Cochran, who created the role in the play’s London premiere, was a last-minute replacement for Amanda Plummer, who left the production due to “creative differences.”

But it’s difficult to imagine anybody funkier or better than Cochran as the wary, vulnerable Agnes.

A decade ago, she’d lost her 10-year-old son to a kidnapper, never to find him again; her ex-husband (Michael Cullen) has just gotten out of jail and is pestering her.

Then a friend (Amy Landecker) stops by with the handsome but decidedly odd Peter (Michael Shannon, in a terrific performance).

Agnes takes a shine to him, inviting him to stay, but over the next few days, his bizarre world-view emerges. He’s convinced his mind has been messed with by the Army, and eventually envelopes Agnes in his own delusions.

“Bug” is a fantasy about paranoia, but under the meticulous if slightly cuckoo direction of Dexter Bullard, it’s less a play than an obsessive stunt designed to entrap and humiliate its characters.

That said, Letts creates some richly pathetic people, whom Cochran and Shannon bring to vivid life.