By Joseph McDonough
Enquirer contributor

DAYTON - Proof is here, there, everywhere.

The 2001 Pulitzer Prize and Tony award-winning play by David Auburn was seen at the Playhouse in the Park a month ago. It has also been staged this year at Actors Theatre of Louisville, the Cleveland Playhouse and now in a solid production at the Human Race Theatre in Dayton, directed by the University of Cincinnati's Richard Hess.

There are several reasons why Proof is the most produced new play in America, with 29 productions at regional theaters this season alone, according to American Theatre magazine.

Auburn's tale of family relationships and mathematical proofs is alternatingly funny and moving with a little bit of mystery. The play has great characters and is tightly written, with a few surprises that keep audiences enthralled.

The story centers around Catherine, the daughter of a mathematician who may or may not have inherited her father's genius - as well as his mental instability.

Cincinnati theatergoers will recognize Joneal Joplin as the enigmatic father (and real life dad) of worried Catherine (a splendid Jennifer Joplin). The elder Joplin can practically claim Ohio residence, having already starred in Ah, Wilderness! and A Christmas Carol at the Playhouse and Copenhagen at ETC this season.

Here he gives another fine turn as he displays warm, fatherly reassurance in the first act, then the fragile ebbs and flows of a troubled mind as we learn more about him in Act 2. He has a wonderful little moment as he relates the tiny joys of watching people rummage through old books at a bookstore.

As Catherine, Jennifer Joplin is equally engaging and expressive as a lonely young woman afraid of herself and the future, yet confident enough in her intellect that she hasn't given up hope.

Teresa Kelsey is dead on as Catherine's control freak sister, yet manages to display a sincere sisterly concern.

The strong cast is rounded out by Brad Light as the likeably energetic (though a tad whiny at times) grad student, math geek and bad musician who becomes romantically involved with Catherine.

Mark Halpin (fresh off a terrific set design for UC's College-Conservatory of Music's The Wild Party) delivers an appropriately dilapidated back porch and yard of an old neglected Chicago home.

If you missed Proof earlier at the Playhouse (or if you want to see it again), make the short drive to Dayton to see for yourself why audiences enjoy this play.

Proof, through March 30, Human Race Theatre Company, (937) 228-3630.