Let's give credit where credit is due: By staging Euripides' rarely performed tear-jerker "Ion," which dates back to circa 410 B.C., Natural Theatricals has valiantly shone a light into the more obscure reaches of the classical canon. With its three-hankie lineup of mistaken identities, near-murders and surprisingly sunny twists, "Ion" stretches the conventional definition of Greek tragedy: Audiences bred on the likes of "Oedipus the King" and "Antigone" may raise their eyebrows at the ultimately happy fate of Kreousa, an Athenian queen who was once raped by Apollo and who subsequently abandoned the baby she bore.

As noteworthy as "Ion's" tonal ambivalence is the thrilling venue that houses this particular production: the soaring Greek Revival indoor amphitheater, with art deco touches, nestled at the heart of the George Washington Masonic National Memorial. Alas, other than noble intent and felicitous choice of location, director Brian Alprin and his team don't bring a lot to "Ion."

With the exception of the odd tolerable moment, the acting of the 10-person cast is lousy -- the delivery sometimes histrionic and sometimes stilted, the expressions and gestures so exaggerated they balloon the play's more melodramatic aspects.

Typically overblown, for example, is Paula Alprin's portrait of Kreousa, who re-encounters her son, Ion, once he's grown to become an attendant at Apollo's temple in Delphi. Though Alprin carries herself regally and looks imposing in a diadem that might have been lifted from a Cecil B. De Mille epic, she tends to indicate emotion by portentously widening her eyes, a tic that often gives her the look of a horrified heroine in a schlocky silent movie.

Michael McDonnell doesn't impose the same staginess on his character, the devout and innocent Ion, but he gives the youth all the energy and charisma of a wet noodle. And there's a stunning lack of chemistry between him and Manolo Santalla, who camps it up as Kreousa's husband, Xouthos, so it's pretty hard to buy the potentially bittersweet scene in which Xouthos offers to adopt Ion.

Tiffany Givens does lend epicene dignity to the role of Hermes, and Tom Neubauer is fitfully entertaining as Kreousa's bloodthirsty, aged tutor. As for the four-member chorus: Danielle A. Drakes stands and speaks with poise, but the other actresses can be painful to watch, with their bad habit of leaning forward to emphasize urgency and passion.

Michael Null's simple set -- white faux-marble pedestals, a white statue, gold vases, a green screen -- harmonizes nicely with the amphitheater's decor. The same cannot be said for Rip Claassen's excruciatingly kitschy costumes, which look as if they've been patterned after the tunics and togas in the Asterix comic books.

Perhaps Natural Theatricals will do more quality control on its next two offerings: Archibald MacLeish's "Herakles" and Paula Alprin's mythology-inspired "Alexa's Necklace." Certainly the company's current focus -- mounting both Greek classics and new plays that take up ancient Greek themes -- is interesting and deserves a laurel or two.

Ion, by Euripides, translated by Deborah H. Roberts. Directed by Brian Alprin. Lighting, Franklin C. Coleman; music, Ellen Taaffe Zwilich. Approximately two hours. At the George Washington Masonic National Memorial, 101 Callahan Dr., Alexandria. Call 703-739-5895 or visit www.naturaltheatricals.com.

Michael McDonnell and Paula Alprin are a couple of lowlights in Euripides' "Ion," at the George Washington Masonic National Memorial.