Composer Daniel Turnbull serves double duty as he performs his own music on the guitar and harmonica for A Lie of the Mind.

Sam Shepard’s A Lie of the Mind is a play about delusion. It’s difficult to write a play about delusion, and it’s equally tricky to stage one. It’s usually not too hard to get an audience to relate to a story about sane characters in normal situations, but anybody who stages a play about delusion doesn’t have the benefit of that automatic connection with the audience. Instead, that connection has to be established by the company in other ways: by keeping the play’s pace as brisk as can be, by making its themes and symbols clear and satisfying and by making sure that all artistic elements beyond the text are as riveting as can be. It is easy to get hooked by a boy-meets-girl story; it’s a lot harder to get interested in the sight of a lucid, crippled man screaming for help while two characters blindly yammer about flag-folding right beside him.

But that flag-folding scene is a perfectly typical scenario in A Lie of the Mind, which was staged at Zero Church Street last weekend by the American Repertory Theater and the Moscow Art Theatre School Institute for Advanced Theatre Training (ART/MXAT). The production itself was not a bad one; I’d be happy to see most of its company in a play that was grounded in sanity and realism. But watching them take on A Lie of the Mind only emphasized that many of its actors were still learning how to make complicated characters believable, and that together they could not effectively elucidate Shepard’s complex themes.

A Lie of the Mind contains multiple, parallel tales of family crisis with Jake (Patrick McCaffrey), a stubborn, malicious paranoiac with a bad memory as their uniting element. As the play begins, he has badly beaten his wife, Beth (Nichole Shalhoub), and run off, thinking that he’s killed her. However, a doleful Beth has survived and is recuperating with the help of her brother, Mike (Tor Hillhouse). Also in the mix are Jake’s clearheaded siblings (Jodi Dick and Kaolin Bass) and a trio of daffy parents (Francesca Carlin, Tug Coker, and Laura Nordin).

There is willful deception in this play, as well as self-deception. There is illogic and irrationality and pretentious dialogue sprinkled with Western slang. There are cumbersome metaphors galore (the goat, the burning barrel, the model airplanes). In short, the play needs a nuanced and delicate touch to prevent it from becoming dense and dull, which this company could not provide.

Nonetheless there were a number of worthy elements in the show. Dick showed perhaps the best instincts in the cast: when she started talking and stopped talking, it felt natural and unforced, not something merely demanded by the script. Hillhouse had many fine moments, exhibiting a crisp, clear voice and a talent for knowing how to throw away a line to get a laugh. Shalhoub handled Beth’s vocal and physical handicaps expertly throughout the show, and Bass offered the right note of impassioned incredulity as Beth’s unwilling love interest.

Offstage, composer Daniel Turnbull performed the show’s wry, Western-tinged score from his front-row seat, pulling double duty on guitar and harmonica. His riffs meshed well with the show’s ably unhinged sound design and Nick Vargelis’ lighting.

The blame for the show’s flaws can probably be placed with director Robert Walsh, who was ultimately responsible for making sure that the show was as comprehensible and convincing as possible. But the lead performance from McCaffrey, whose Jake could have used some toughening did not help; McCaffrey diluted the role with too much tenderness, and in the process he turned Jake into a petulant bore. The play’s three elderly characters were likewise lacking in interpretation; each of the three actors had occasional moments of comic vigor, yet they did not have the presence required to make their irrational characters compelling.

The Institute’s company initially raised the bar very high by taking on A Lie of the Mind. Their good intentions and talent notwithstanding, the show’s two-and-a-half hours were neither enjoyable nor enlightening.

—Crimson arts reviewer Benjamin J. Soskin can be reached at bsoskin@fas.harvard.edu.