Okay, so you might want to cancel those Halloween party plans and stay in on Friday night.

This week's 20/20 promises to be a must-watch, thanks to an interview with Leah Remini. The actress will open up about her decision to leave the Church of Scientology in 2013, which she details in her new book, Troublemaker: Surviving Hollywood and Scientology (on sale November 3).

Remini had originally cited wanting to spend more time with her daughter as the main reason behind her split from the controversial religion, but sheds more light on other factors that contributed to her decision. Those include doubts over church leader David Miscavige and fallout over criticism about actor and prominent Scientologist Tom Cruise.

"Being critical of Tom Cruise is being critical of Scientology itself," Remini revealed in a sneak peek of Friday's interview. "You are evil."

Remini, who joined the church with her family at age 15, also said the religion made her lose perspective.

"As time goes on, you start to lose touch with the real world," she shared. "The mindset becomes us against them.

"The decision to leave is...you're giving up everything you have worked for your whole life," she added. "I feel that people need to understand this has been my whole life and I want them to understand how it happens."

Watch the preview clip below.