Hal (Alec Williams) chats with Catherine (Cera Naccarato) in “Proof” at the Tornabene Theatre through Feb. 26.

Ed Flores

Grief, deep and dangerous, holds hands with genius and madness in David Auburn’s “Proof,” now on stage at Arizona Repertory Theatre.

And it makes for some riveting theater.

The four-character play snagged the Tony and Pulitzer prizes and it’s easy to see why: Auburn’s script is tight, suspenseful, and has a most satisfying arc.

Director Hank Stratton has put together a cast that gets the rhythm and the nuance of this story about a mathematician, his daughters, and a former student of his.

That sort of boils it down to the mundane, and this play is anything but.

Catherine (Cera Naccarato) has become the caretaker for her father, Robert (David Morden), a once-brilliant mathematician who has gone slowly mad. She, too, may have the chops to be a brilliant mathematician. And is, perhaps, on the verge of madness herself.

The play opens a few days after his death, and he’s sitting on the back porch of their Chicago home, visiting with her. That she is talking to the dead could be the insanity creeping up on her, and she’s well aware of that. Or it could speak to the depth of her grief — who hasn’t lost a much loved person and imagined chats with them after they are gone?

Her father’s final years were spent writing gibberish in notebooks. But a former student, Hal (Alec Williams), can’t imagine that Robert didn’t write some mathematical brilliance. He spends his days in the house poring over his prof’s notebooks, convinced that his genius could not have disappeared so quickly. At the same time, his attraction to Catherine grows.

Enter Clare (Kelly Hajek), Catherine’s hyper-efficient older sister who believes her way is the only way. And she’s convinced that Catherine, indeed, has inherited Daddy’s unraveling mind. She’s determined to whisk her back to New York, set her up with an apartment and a shrink, and assuage her guilt for allowing Cathering to carry the weight of caring for Dad.

“Proof” is packed with family drama. But it also explores issues of trust, integrity, and oppressive guilt.

And the cast is impressive. Especially Hajek, who handled the officious Clare character like a pro — that’s surprising as she’s just a sophomore. It’ll be exciting to watch her journey at the UA. Naccarato’s Catherine had a rich interior life and Williams owned the geekiness of a clumsy Romeo in love with math. Morden, the only non-student in the cast — he’s an assistant theater prof — cuts a fine father figure.

“Proof” is funny, heartbreaking and suspenseful. And it offers a look at the impressive talent at the UA.

Contact reporter Kathleen Allen at kallen@tucson.com or 573-4128.