Our movie critic's weekend selections

Clouds of Sils Maria. Juliette Binoche and Kristen Stewart star as a famous actress in midlife - and still, she hopes, in mid-career - and her personal assistant, half her age and full of restless intelligence. As Binoche rehearses for a new role in a hideaway in the Swiss Alps, Stewart's character takes on the other part, and the women's relationship begins to mirror the one they're acting. A meditation on memory, on growing older, on the life of the theater, and the theater of life. From filmmaker Olivier Assayas. R

Ex Machina. Alex Garland's forward-looking, unsettling sci-fi thriller stars Oscar Isaac as the billionaire inventor of a sentient robot, Domhnall Gleeson as the whiz-kid programmer invited to run the 'bot through a series of tests, and Alicia Vikander as Ava, the cyber-creature in question. Is she true A.I.? And if she is, what does that mean for humankind? R

While We're Young. Ben Stiller and Naomi Watts are a married couple in their mid-40s who befriend a twentysomething hipster duo, played by Adam Driver and Amanda Seyfried, in Noah Baumbach's cuttingly comic, keenly observed meditation on generational longing, and on acting your age - and not. R