Every Brilliant Thing gives its central character a highly unusual challenge. In St. Louis Shakespeare’s absorbing production, Isaiah DiLorenzo surmounts that challenge with apparent ease that is surely the result of extremely hard work with the director, Donna Northcott.

DiLorenzo’s character is making “a list of everything brilliant about the world. Everything worth living for.” The list maker starts his compilation when he is seven years old as a coping mechanism after his mother’s attempted suicide. (The use of masculine pronouns for the list maker is appropriate for St. Louis Shakespeare’s staging, but the script states the part “can be played by a woman or a man of any ethnicity.”)

The list grows longer and longer as its maker grows older because he never stops having to deal with the effects of chronic depression—his mother’s and his own.

The list maker is the only scripted performer—but not only performer—in the play written by Douglas Macmillan with Jonny Donahue. The play is an adaptation of Macmillan’s short story, “Sleeve Notes.” He worked for over a decade with George Perrin on turning the story into a full-length play. Macmillan acknowledges in the script that Donahue “essentially co-authored the play while performing it” by drawing “on his experience as a stand-up comedian to find ways to tell the story and use the audience” that the other collaborators “couldn’t have conceived of.”

No two performances Every Brilliant Thing will ever be the same. The script challenges the list maker to recruit seven members of the audience to play significant roles in the play. One draftee is given one word to say in response to everything. The others are allowed to say whatever they want. The list maker must go with whatever is said.

Other members of the audience participate, too. Before the show begins, the list maker distributes quite a few numbered cards on which one item from the list is written. The cardholders are told to read what is on the card when the list maker calls out its number. If the cardholder misses the cue, an offstage member of the company fills in the gap.

DiLorenzo captures the full range of the list maker’s emotions throughout the play, but this admirable achievement is no more than half the battle in Every Brilliant Thing. More important to the show’s success is DiLorenzo’s mastery of improvising with others.

The conscripted members of the audience on opening night were not the most polished of performers, but they all made concerted efforts and improved as they went along. DiLorenzo’s responsiveness to his scene partners coaxed the best out of them, mainly with gentle affirmation, but also with a touch of firmness when required.

The production does not have a set, and the houselights are always on. John “JT” Taylor’s sound and Amanda Handle’s props make helpful contributions to the show.

Recognizing the difficulty of the play’s subject matter for some viewers, St. Louis Shakespeare thoughtfully devotes the back page of its program to a list of crisis intervention and suicide prevention hotlines.

Every Brilliant Thing continues through June 26 at The Chapel, 6238 Alexander Drive.

—Gerry Kowarsky