Such a concept is presented in “Mindgame,” the first play of the Next Act Theatre’s 2003-’04 season. The plot twists and turns, with one shock after another smacking the audience in the face and leaving viewers questioning even their own sanity by the play’s conclusion.

Mark Styler (Shawn Douglass) is a “true crime” writer who is fascinated by the minds of murderers. He’s already written two books on the subject, with each one focusing on a specific killer, and now he’s interested in pursuing a series of interviews with one of the nation’s most notorious murderers: Easterman.

Standing between Styler and his interview, though, is the mysterious Dr. Farquhar (David Cecsarini), the head of Fairfields Asylum and Easterman’s keeper. The good doctor is evasive about the nature of his off-beat hospital and becomes terse when Styler expresses the nature of his visit.

What follows is a well-paced interchange between the two men that opens the closet door to unleash all kinds of skeletons. Although some of the secrets revealed are a bit predictable, the course taken by Anthony Horowitz’s script in exposing them is far from expected.

However, it’s not just an innovative script that makes “Mindgame” so good. It’s also supported by stellar performances by Douglass, Cecsarini and Tami Workentin, who plays Nurse Plimpton, a nurse in the institution who at first glance is slightly nutty but later proves that appearances can be deceiving.

Douglass becomes the one stable element on a stage full of chaos. His nervousness resulting from the sketchy people around him, coupled with his human desire to get to the bottom of the mysterious asylum, makes him someone to whom audience members can relate. Each time he tugs nervously at his briefcase or scoots anxiously away from the other, highly neurotic characters, viewers feel the same twinges of anxiety he so clearly demonstrates.

Also impressive is the turn Cecsarini takes as the disturbing doctor. He flits comfortably between the different mood swings of his character, easing from suave and confident to fretful and ill at ease. So convincing is his portrayal, in fact, that by the play’s end viewers will leave questioning even their own sanity, not to mention that of the people they just watched on stage.

Although she does not share as much stage time as Douglass and Cecsarini, Workentin makes good use of what she is given. Her dramatic entrances and exits provide a satisfying breather from the intense exchanges between the two gentlemen, and she has a flair for capturing the spotlight without monopolizing it.

A particularly notable section of dialogue in the script involves Farquhar explaining to Styler that, when a person has gone mad, at times he hears others’ conversations as gibberish. Perhaps instead of “Would you like a glass of water?” the words are understood as “Wallpaper cigarette toothpaste, chewing gum?” But, is it really the so-called madman who is hearing the gibberish? Or is his position in the straitjacket that allows others to tell him he is simply confusing their words, when really it is they who are insane?

In addition to Horowitz’s superb script and impressive direction by Kurt Hartwig, “Mindgame” relies on subtleties scattered throughout the performance that fully enrich the production. For instance, just as the first act reaches its conclusion, one of the script’s integral plot turns comes to life. In order to convey the change that has taken place for the start of the second act, audience members returning from intermission see a slightly different set than the one they left.

Scenic designer Rick Graham exchanged a painting of a friendly puppy above the office fireplace for one of a fierce-looking wolf; the telephone and visitor’s chair have each been replaced with ones that are slightly more institutional in nature; and the inviting cushion on the window seat is now gone. The differences help the audience transition from the interior of one man’s mind to another’s, a necessary evolution at the start of the new act.

“Mindgame” combines a compelling script with phenomenal performances and assorted intricacies sprinkled over the course of the play to produce a show that leaves viewers both satisfied and scratching their heads, walking away with something to ponder.

After all, is it the man in the straitjacket who is insane? Or wallpaper cigarette toothpaste, chewing gum?