The former High School Musical star admits he was looking for a project with depth and risk - and he found it in Lee Daniels' steamy new film.
But there was one explicit scene that left him stunned - as co-star John Cusack's character is so turned on by Kidman's Charlotte Bless he masturbates into his underwear as Efron's Jack Jansen watches.
The young star tells Black Book magazine it was a very intense shoot: "That was the first day of filming and Nicole just completely went for it. She was telling everyone, 'I'm bringing my A-game. What do you have?'
"I've never been so scared in my life, but that moment affirmed this movie was everything I set out to do."