PARK CITY, Utah — Glenn Close is returning to theater after more than 15 years — and it won’t be in a musical.

“I am planning a play in the fall,” Close said in an interview Monday at the Sundance Film Festival, where she’s promoting the film “Low Down.”

The 66-year-old actress, a part-time resident of Scarborough, Maine, wouldn’t say what play she’s joining in advance of the official announcement.

“I’m not sure what the producer’s plan is. I think he might want more of a cast before,” Close said.

However, she hinted: “The world that it is in is a world I know very well. It’s just a very complex play. It’s very challenging. It’s like somebody said, ‘A mountain of a play.’ I’m not coming back in a musical.”

Close, a three-time Tony winner, started in theater before moving to film and TV, including the series “Damages.” She last appeared on Broadway in “Sunset Boulevard.”