It’s an intriguing proposition for a play: two actors meet for the first time on stage. One, the First Actor,  has rehearsed the play, while the Second Actor has never even read it.

In An Oak Tree, this dynamic repeats for each day’s performance – 22 in all by the time it ends its run on December 9 - with a freshly cast Second Actor encountering anew the script, the audience, and the actor he plays against.

Written by Tim Crouch, An Oak Tree is also a daring exercise in dramatic abstraction, and a multi-layered exploration of meta-theatrical performance.

The storyline gives a suggestion of how An Oak Tree plays out. The First Actor is a stage hypnotist (played by Gage Wallace with tremendous precision and verve), putting on shows that incorporate audience participation - giving us the first of those meta layers, a “show within the show.”

The dramatic tension rises as we learn that First Actor’s little girl has been killed in a car accident, and that Second Actor is the responsible party. Calling for volunteers from the audience (but it’s another layer, an imaginary audience - we live patrons were warned at the outset not to volunteer), the First Actor sees among the audience volunteers the very driver (the Second Actor) who killed the little girl.

First Actor’s grief and anger rise. He hypnotizes Second Actor and puts him through a series of demeaning exercises, including an admission of guilt for the act. The eight other volunteers (none are visible, of course) are dismissed, so that only Second Actor and First Actor remain.

The dynamics become ugly between First Actor and the hypnotized Second Actor, who slips in and out of awareness in this scene, and there is increasing discomfit between the two characters. We feel the discomfort as well, and witness a shift in power between the characters as the scene progresses.

So how does a non-scripted character perform his or her role (both men and women are cast as Second Actor, including Alejandro Tey the night I saw the show). Actors are freewheeling spirits, generally – but they do like to rehearse the script, and to be prepared before they enter the stage. An Oak Tree has elements of improvisational performance and sight-reading of lines. These 22 venturesome Second Actors – Alejandro Tey showed his quick wit and deft dramatic skills - have willingly subjected themselves to the trial devised by Crouch's play.

As to practicalities of producing the show, Crouch and director Jeremy Aluma allow First Actor to brief the real live audience on some background, and their role, as the show commences. When Second Actor is introduced, he or she is given two or three pages of dialog to read from directly, at various points. And Second Actor also wears an audio device to receive whispered verbal cues from First Actor, who at other times offers those cues and prompts aloud, or whispers them into the ear of Second Actor.

This one-hour show by Red Theater is provocative and intriguing, even mind-bending for avid theater goers. It will have you thinking about it for days afterward. An Oak Tree is at Chicago's Athenaeum Theatre through December 9.