To begin with, you will not doubt for an instant that Kansas University student Aaron Champion is a middle-aged, middle-European Jew, nor that recent graduate Summer Eglinski is a rural southern Missourian. Both live so fully in their parts and speak so unerringly in their dialects that the illusion is complete and never broken. Playwright Lanford Wilson, himself a Missourian, has perfect pitch for the nuances of both characters’ habits of speech and thought.

These two are the entire cast of the Pulitzer Prize-winning (1979) “Talley’s Folly,” set in July 1944, somewhere near Lebanon, Mo. The action takes place around an ornate boathouse, the “folly,” on the Talley farm, with the audience sitting (as the opening monologue tells them) “in the river.” Champion, as Matthew Friedman, has come to visit Sally Talley (Eglinski), the 31-year-old daughter of a family of Ozark aristocrats, part-owners of a local garment factory.

The audience at first senses, then learns definitively, that Matt has come from St. Louis to court Sally; and the play is his courtship. In fact, he has returned, after spending several days in her company the previous summer. He even had dinner with the family, resulting in her father’s claim that “that man’s more dangerous than Roosevelt himself!” Matt sums himself up in the family’s eyes as a “communist infidel.”

Sally is enigmatic – Matt calls her a “puzzle” and a “mystery” – evidently enjoying his presence when he’s not looking, but brushing off his attempts at rapport. She refuses to answer his questions (for example, “What are you afraid of?”) and repeatedly asks him to leave – yet she does not leave. Eglinski handles Sally’s moods splendidly: amusement, bemusement, pique, flirtation, fury, heartbreak and, above all, evasiveness. She makes believable Sally’s blend of country girl and nurse and college graduate and budding progressive (Sally read Thorsten Veblen to her Sunday-school class).

Matt professes romantic naivete, but is nevertheless ingenious and persevering. He tries modesty, wit, earnestness, slapstick, mimicry and even frontal verbal attack, challenging Sally to deny that she loves him. He’s also as good at evasion as she is, spinning parables about his identity (“a possible Lithuanian”) to resist her probing. Champion’s role is a tour de force as he speaks almost nonstop for more than an hour and a half without intermission, never misplacing an accent or omitting a mannerism that defines his character. He eloquently conveys Matt’s frustration and longing.

Director Dennis Christilles has set high standards for this talented pair, and they have lived up to them. Mark Reaney’s charming set conveys the mystery of the characters’ personalities and the sensuality of the summer night on the river. Tim Boeshaar’s lighting is effective, complete with moonlight reflected from the river’s ripples.

Sally’s aunt Charlotte has told Matt that “there’s something you don’t know … something only Sally can tell you.” The play’s hour and a half passes quickly as this complex and difficult couple spar, round after round, to determine whether Sally will tell him. You’ll have to see the play to find out, and in a powerful final scene, you’ll be glad you did.