Anne Heche's troubled Catherine will get a new suitor in Broadway's Proof Oct. 8 when Stephen Kunken steps into the role of quirky math whiz Hal, taking over for Neil Patrick Harris, who exited Oct. 6.

Harris, making his debut on Broadway, joined the production at the Walter Kerr Theatre July 2, when an entirely new company — Heche, Len Cariou and Kate Jennings Grant — took on the roles penned by David Auburn.

Juilliard grad and native Long Islander Kunken is no stranger to the play: He stepped into the Broadway staging during the run of the original cast in 2001, playing opposite Mary-Louise Parker. He was also Hal in the 2001-02 national tour that ended in June.

In the play, Heche, whose own emotional turbulence has been documented in her memoir, "Call Me Crazy," plays frazzled Catherine, the daughter of a math genius (played by Cariou) who may have inherited her father's gift — and illness. The Pulitzer Prize-winning play by Auburn (who also won the Tony) has been celebrated by critics and audiences as a romance, a drama of splintered family dynamics and a mystery. (Crowds still gasp at the Act One curtain line.)

Heche has earned solid reviews for this, her Broadway debut. It is thought that Proof, which has long since made its investment back, will likely end by January 2003, the time when business traditionally dips on Broadway. No official closing date has been announced. The week of Sept. 23-29, the average attendance at the Walter Kerr Theatre was a respectable 62.7 percent of capacity, according to figures supplied by the League of American Theatres and Producers. *

The company remains under the direction of Daniel Sullivan, who won a Tony Award helming the work.

Kunken's Off-Broadway credits include Arthur Laurents' Home of the Brave, Tony Kushner's The Dybbuk, Misalliance and Henry VIII.

Grant was seen in the Encores! concert of Bloomer Girl, on tour in Finian's Rainbow and in Off Broadway's Summer of '42.

Mary-Louise Parker (Prelude to a Kiss, "Fried Green Tomatoes") created the central role in the play when it began Off-Broadway at Manhattan Theatre Club May 23, 2000. She won the Best Actress Tony when it moved to the Kerr Theatre in 2000-2001.

The entire original cast was Tony nommed for its work.

Len Cariou brings with him the weight of past productions of Shakespeare and Sweeney Todd. Cariou's most recent Broadway turn was as a bitter husband in Neil Simon's The Dinner Party. He won a Tony Award for the title role in Sweeney Todd and was Tony nommed for Applause and A Little Night Music. His credits include works at the famed Stratford Festival in Ontario.

The Proof national tour, led by Chelsea Altman and Robert Foxworth, with Stephen Kunken and Tasha Lawrence, ended June 23 at the Auditorium Theatre in Denver. Regional theatres are already starting to produce resident productions of the work. Around the country this season, Proof is the most-produced title in professional resident theatres. Regionally, it's expected to be one of the most-produced plays of the decade. (The fact that there's one set and a cast of four helps.)

Proof is produced on Broadway by Manhattan Theatre Club (Lynne Meadow, artistic director; Barry Grove, Executive Producer), Roger Berlind, Carole Shorenstein Hays, Jujamcyn Theatres, Ostar Enterprises, Inc., Daryl Roth and Stuart Thompson.

The Walter Kerr Theatre is at 219 W. 48th Street. Tickets are $24-$75. For information, call (212) 239-6200.