'Swan Song' review: Mahershala Ali's powerful performance powers cloning drama

WHAT IT’S ABOUT Mahershala Ali stars in this sci-fi drama that engages with one of the most timeless philosophical inquiries.

The two-time Oscar winner ("Moonlight," "Green Book") plays Cameron Turner, a husband and father stricken with a terminal illness that he’s hidden from his wife Poppy (Naomie Harris) and adolescent son Cory (Dax Rey).

There’s a chance he might never have to reveal it: it’s the near future, and Cameron has been given the opportunity to be one of the first participants in a cloning program overseen by Dr. Jo Scott (Glenn Close).

The pitch: Scott’s team designs a healthy clone that’s identical to Cameron except for a single birthmark, infuses him with the exact same memories (even the subconscious ones) and seamlessly replaces the original person with this new version. The switch remains top-secret and the family never knows the difference.

The drama finds Cameron wrestling with the weight of this ethical dilemma. It’s written and directed by Benjamin Cleary, himself an Oscar winner for his short film "Stutterer."

MY SAY The moral quandaries manifest in cloning have provided the grist for so many works of popular art that it would be all but impossible for "Swan Song" to have anything provocative to say about the subject.

The writer-director recognizes that he doesn't need to take the familiar narrative in an unexpected direction, or to push the boundaries of the form by inventing a whole new filmmaking style.

Cleary's goal seems simpler than that, but no less noble: to tell a powerful story that resonates emotionally, and to use the framework of cloning in service of a study of grief and acceptance of mortality.

The key toward making it work lies entirely within the extraordinarily able hands of its star.

This is a demanding acting job: Ali must invest Cameron and his clone with inner lives that are at once recognizable but also distinctly their own, while playing intense dramatic scenes opposite himself. The most basic notions explored in this story depend on the ways in which the actor frames each person.

Unsurprisingly, he's up for the challenge.

Cameron struggles to find a way to accept the inevitable: that he will have to let go of his wife and son without ever getting the chance to say goodbye, as the cloning program requires that they do not know about it. The star plays him as a man who is beset by turmoil: stricken with despair and struggling with the fundamental dishonesty of it all.

His clone, aware of the reason for his existence, looks and sounds exactly the same, but Ali tweaks the ways in which he reacts to the situation to replace Cameron's sadness with something closer to patience and empathy.

It's an impressive balancing act, to craft two clearly defined characters out of these circumstances, and it allows for the movie to ask its familiar questions about how we define our humanity in a new way.

BOTTOM LINE Mahershala Ali's remarkable performance makes "Swan Song" worth seeing.