They don’t call it “star power” for nothing!  The musical Herringbone is a worthy, intriguing show that takes too many detours, and ultimately runs out of gas before coming to a full stop (more on that later.)  But when Ben Dibble takes center stage – which, fortunately for us, is pretty much every second of the show – it’s absolutely riveting.

It must be two decades ago that I first saw Dibble, who while still a college student had dazzled the crowd at a Barrymore award presentation when he sang a number from Floyd Collins.  From the start, it was clear that his gifts were not only prodigious, but wide ranging, even a bit quirky.  He sings beautifully, moves gracefully, and can look like a leading man – but a minute later, he’s also a master of funny faces and comic business.   Part heart-throb, part operetta baritone, part boy next door, part unpredictable character actor.   The only problem was finding a role that could showcase it all.

Fortunately for Ben, he got one early on – Bat Boy was a superb performance, as well as promise of even greater things to come.  Since then, Ben has done fine work in hugely varied musicals and plays, each of which revealed some facets of his art.

But he didn’t have a single vehicle where they could all come together – till now.  This alone makes Herringbone treasurable.

To be fair, it’s more than that – sometimes, problematically, way too much more.  The core of the show is a Depression era biography of a gifted child performer, whose potential career in vaudeville offers a thin thread of hope to his destitute family.  It’s a poignant theme, recalling Day of the Locust and They Shoot Horses, Don’t They, and the evocative, 1920s-tinged music (by Skip Kennon) and mordant lyrics (by Ellen Fitzhugh) keep things on track.  Director Bill Fennelly and his excellent design team have given it a moody, atmospheric production.

Alas, in Act II, the story has turned creepier but also less interesting.  Ultimately, too many (you should forgive the expression) red herrings cause the piece to lose focus.

Did I mention that Dibble plays virtually all the roles?  (Not quite all, though – he’s ably assisted by Dan Kazemi, a terrific pianist/actor/singer, and two other crackerjack musicians).  Anyway, he’s a wonder.

But for all the virtuosity, what’s even more impressive – and will stick with you for a long time – is how much substance he finds in the emotional underpinnings of the character.  There are moments when his expressive face and huge eyes (almost Eddie Cantor “banjo eyes”) capture a sense of baleful nothingness that will take your breath away.

For Ben Dibble alone, Herringbone is a must-see – and how thrilling to say that in July, before the theatre season has officially started!   Which gives me a chance for one last huzzah – hats off to the clever folks at Flashpoint Theatre, for the brilliant idea of a summer season, something Philly’s needed for many years.

Through July 27, Off-Broad Street Theatre, 1636 Sansom St., www.flashpointheatre.org