It’s the natural right of those adapting a book to stage or screen to tweak the original, and often even to make many changes to offer a new approach. Sometimes, that works to enhance our appreciation of the source. In the case of Rachel Wagstaff’s play version of Agatha Christie’s The Mirror Crack’d, now onstage at Asolo Rep, one wishes that Wagstaff had left well enough alone.

Oh, the main characters and the plotline adhere well enough to Christie’s book featuring her beloved spinster sleuth Miss Marple. Besides Marple herself (played here by Suzanne Grodner), there’s a police inspector well known to her, a troubled film star, her director husband, her loyal staff, a longtime female friend of Marple’s, etc. And the mystery, after a brief opening scene, begins the same way: A babbling fan of the star dies after sipping a poisoned drink at a party at the star’s home. Whodunnit and why? Was it meant to kill her, or the actress? Can Miss Marple, who frequently declares that her success in detection stems simply from knowing people, solve the crime?

Well, of course she can. But in Wagstaff’s adaptation, she’s hampered by being laid up in her St. Mary Mead home with a sprained ankle. That means much of the action here is either narrated or re-enacted for her by the inspector, Craddock (Billy Lyons), or other characters, and the way that’s handled is sometimes as frustrating for the viewer as it must be for Miss Marple. We frequently see the same moment from different angles or characters’ point of view—legitimate enough, but also a bit tedious.

And Wagstaff’s script is heavy on the talk. Faced with a juggernaut of dialogue, the actors seem to be rushing just to get it all out, unable to really spare the time to develop convincing characters or motivations. It doesn’t help that the pacing (under the direction of Michael Donald Edwards) doesn’t provide much variation, either. It just all feels pushed. And Wagstaff’s attempts to draw comparisons between Marple and the actress don’t quite work.

On the plus side, the mystery itself here, if you haven’t read the book or seen other adaptations, is a good one (supposedly based on true events in the film star Gene Tierney’s life, although Christie denied that). Grodner, although not my conception of Marple, has her moments in the role, especially in scenes with Jan Neuberger as her fluttery friend Dolly and sometimes with Lyons as the policeman she’s known since he was a boy. Likewise, Rebecca Watson registers well enough as the actress, Marina—someone who’s so used to how the public perceives her it’s hard to know who she really is.

But overall, this Mirror is a disappointment—a poor reflection, if you’ll pardon the pun, of its inspiration.

The Mirror Crack’d continues through March 14 at Asolo Rep. For tickets, call (941) 351-8000 or visit asolorep.org.