Complete Unknown

Michael Shannon: too tall for the movie.

“Complete Unknown” begins with fractured clips of the same woman — or at least the same actress (Rachel Weisz) — in multiple professions, going by multiple names. Are these fantasies? Past lives? Something else? It’s a discombobulated start for what turns out to be a straightforward, bluesy drama about the identities and life-paths we choose for ourselves.

The always interesting Michael Shannon stars as Tom, a New York academic hosting his birthday party at a time of stress and uncertainty. His cake calls him “Tony.” More importantly, his Iranian wife, Ramina (Azita Ghanizada), is contemplating a career-related move to California, and Tom isn’t sure he’ll go with her.

One of their friends brings a date to the party, one Alice Manning (Weisz), a self-assured woman whom Tom recognizes from his past — except her name wasn’t Alice then. Through much engrossing walk-and-talk action (shades of the “Before Sunrise” trilogy), director Joshua Marston (“Maria Full of Grace”) has Tom — and us — come to see the appeal in Alice’s untethered way of life, her liberating gift for reinventing herself and becoming whomever she pleases. When the two stumble into a situation where they can help an older neighbor couple (the delightful Kathy Bates and Danny Glover), Alice goads Tom into trying it out. Pretend to be a doctor, why not? Make up a backstory! It’s fun!

The simple question at the center of the film is for Tom. Would he like to live free of obligation, with no attachments? Or should he follow the path he’s on, predictable and in some ways predestined, but stable? Weisz plays Alice as a determinedly free-spirited polymath, not a careless flake, while Shannon’s Tom is bemused, annoyed, and fascinated by her. It might be better as a conversation-starter than as cinema, but the film’s astute central performances elevate it.

B (1 hr., 30 min.; R, because they say the F-word four times, and literally no other reason.)