After journeying to Middle-earth together for the “Lord of the Rings” movies, Cate Blanchett and Ian McKellen are playing more grounded roles in this year’s films. In “Mr. Holmes,” McKellen stars as the famous detective in old age. Blanchett pulls double duty in “Carol,” as a 1950s housewife who falls for a younger woman; and in “Truth,” in which she plays embattled “60 Minutes” producer Mary Mapes.

Ian McKellen: “Carol” is a love story, isn’t it?

Cate Blanchett: I don’t know if you’ve read “The Price of Salt.” It was Patricia Highsmith’s first novel. She writes about the really dark recesses of the human mind, which is what I love about her. And all these unpalatable thoughts and obsessions that we all have, but we never give voice to, or admit to anybody. And Phyllis Nagy wrote the most beautiful screenplay.

McKellen: And you...