GREAT BARRINGTON — Watching "Peter and the Starcatcher" at Saint James Place, where the show had its press opening Thursday, you can't help but give the generally youthful members of this GhostLit Repertory Theatre Company cast huge credit for their seemingly inexhaustible supply of energy and invention.

They are bucking a lot. The building, a former church, is sufficient for theater but it has its limitations, particularly in the former sanctuary which, in effect, is Saint James Place's main stage. A smaller space in a room down the hall and to the rear of the sanctuary serves as a reception and meeting room and as a smaller performance space. Sound bounces around this big playing space with almost a will of its own. Voices echo, especially the farther back you sit and, as a result, articulation is swallowed. So, albeit in part because this play's style, for the most part, requires it, the playing style is broad; the vocal projection louder than one might otherwise need. There are those moments when you have to strain to follow the plot, which is full and winding.

"Peter and the Starcatcher" is an origin story — a Peter Pan origin story that plays out on and below the respective decks of two ships at sale on the high sea, The vessels are each carrying one of two identical steamer trunks one containing an unidentified cargo that is said to be valuable to Queen Victoria; the other a decoy carrying sand. The trunk of inestimable value has drawn the attention of the pirate Black Stache (Cody Lee Miller in a showy, self-absorbed performance that comes perilously close to taking over director Caitlin Teeley's otherwise smartly produced show. As it happens, that same trunk has value for young Molly Aster (Caroline Fairweather), apprentice starcatcher to her father, Lord Leonard Aster (Thomas Whaley), who has cautioned Molly to watch over the trunk and deliver it to him whole, despite the obstacles — pirates, thieves, mermaids, shipwreck, a monstrous crocodile dubbed Mister Grin — that stand in her way.

It's Molly's "coming of age," the fulfillment of a mission that will have meaning for her; her gaining of responsibility and maturity that is as much the spine of "Peter and the Starcatcher" as is the tormented orphan boy (Corey Bryant in a compelling, emotionally authentic performance) who will, by the end of the play, emerge as Peter Pan.

The members of this company of 11 play multiple roles and their inventiveness knows few bounds. Human bodies become prop as if they are inert objects. It's simply dandy.

The narrative is interspersed with a few musical numbers, among them the dazzling second act opener performed by a chorus of mermaids quite unlike any you have ever seen, if ever you have seen a mermaid.

Fight director Olivia Wilcox shows a keen appreciation of just how theatrical and compelling a fight scene can be, especially a match between Black Stache and a rival, Billy Shank (Wilcox).

In addition to the acoustics, Teeley's production isn't aided by a lighting design by William Domack that embraces the dark, spotty and shadowy.

This is not a world given to subtlety or nuance. This is, however, a marvelously robust, inventive world that revels in the physical as much as it dwells in the imagination.