Katherine Brandt is a perfectionist bordering on elitist who dismisses anything she doesn't understand.

Which is why, despite her diagnosis of Lou Gehrig's disease, she makes a trip to Germany to unravel a Beethoven mystery.

The great composer's past and Katherine's present play out in Theatre Baton Rouge's production of Moises Kaufman's "33 Variations," opening May 10 in the Studio Theatre.

The play, the final production in this season's City Series, switches from present to Beethoven's time, eventually merging the two worlds as Katherine, played by Jennifer Johnson, comes to terms with her life.

Katherine is a musicologist who admires the complexities of the composers she studies yet doesn't understand the complexities of her daughter, Clara, played by Kaitlyn Stockwell.

Their relationship is cold, yet Clara loves her mother and worries about her traveling to Germany after being diagnosed with amyotrophic lateral sclerosis.

Perhaps Katherine knows this trip is her swan song, but she doesn't acknowledge it; not even after her nurse, Mike, played by Lee Terrebone, warns her the disease is moving quickly through her body. He and Clara share their concerns about Katherine's health and end up dating.

"She doesn't understand this relationship, either," director Shannon Walsh said. "Neither of them thinks she should be traveling to Germany, but as her disease manifests in the play, you also see Beethoven's deafness manifest."

The mystery in question is Beethoven's "Diabelli Variations," a simple theme on which he composed 33 variations. This obsession with a seemingly inconsequential song by a genius composer doesn't make sense to Katherine, and she has to unravel it while battling her disease.

"When you're playing someone with this disease, you have to show respect for the process," Johnson said. "You will see the different stages in the play, where Katherine finally is in a wheelchair. Her speech is affected in the end, but Moises Kaufman does a beautiful job explaining this in his writing of the play."

The story sounds heavy, but Walsh assures it isn't.

"There's so much humor in this play among the characters," she said. "There's also an element of suspense — is she going to find out why Beethoven wrote 33 variations of this song?"

In Katherine's eyes, Beethoven, played by Mike Katchmer, can do no wrong. But as she delves into the music, she realizes when her world merges with Beethoven that he was as human as her daughter and herself.

'33 Variations'

A Theatre Baton Rouge City Series production

WHEN: 7:30 p.m. May 10-12, May 16-19. Sunday matinees at 2 p.m.

WHERE: Theatre Baton Rouge's Studio Theatre, 7155 Florida Blvd.

TICKETS/INFO: $25; $19, students. (225) 924-6496 or theatrebr.org

Follow Robin Miller on Twitter, @rmillerbr.