My son has only been at daycare for two months, and every day brings its own worries. Parents of older kids probably know it just as acutely. Anything can happen, right? An illness, an accident, a bully. In the United States, particularly, those worries includes an active shooter. It may be statistically unlikely, but that doesn’t really matter, does it? There are days where you think about what you would do if your child experienced that. Or if you lost them. Then there are days where you worry about your child being the one who perpetrates it, no matter how hard you try to be a good parent. These are just thoughts that cross the mind. Stray anxieties.

Those anxieties fuel Fran Kranz’s Mass, a stellar chamber drama about the parents of a shooting victim meeting with the parents of his teenaged killer. Jay (Jason Isaacs) and Gail (Martha Plimpton) are the parents of Evan, one of seven students shot by Hayden, described in the media as a “quiet kid” with dark tendencies who spent a disproportionate amount of time playing online games. Hayden’s parents, Linda (Ann Dowd) and Richard (Reed Birney), still wonder what they did wrong. What could they have done to stop it?

The mediated confrontation of these two couples comes six years after the shooting, and Kranz delivers on the premise by crafting four complicated, deeply hurt parents still reeling from the emptiness of their sons’ absences. Jay has become an activist to prevent further gun violence, although he hates that term to describe himself. Gail has focused on raising their daughter, who hasn’t slept a full night in a half-dozen years. Linda and Richard have been just as battered: They continue to receive mail wishing them death, or worse, and also mail that empathizes with their pain. The loss of their son is combined with their guilt over the lives he took. Neither begs for forgiveness from Jay and Gail, only some solace and understanding.

As the afternoon transpires, the four trade pleasantries, barbs, and stories about their sons. They unpack what could have led Hayden to commit such a heinous crime. Was he evil? A psychopath? Was it preventable? There were warning signs, but what could they have done in the moment? Did Linda and Richard’s love for him blind them to his danger? Richard doesn’t own guns. The weapons used were stolen from a friend’s father. What if they had searched his bed the night before and found them? If only, if only.

In the moment Hayden circled back to Evan’s classroom to fire more rounds into a mass of frightened, dying teenagers — when he looked a pleading boy straight in the eyes and shot him in the head — was that an act of hate? Apathy? Evil? These are questions without answers, only perspectives delivered by parents who will never heal from what happened to their children and how it broke them.

Given the weight of the premise and questions asked, a lesser ensemble or a less delicate script could’ve led Mass into thorny territory. Isaacs, Plimpton, Dowd and Birney are all tremendous in their roles, each with at least one stunning moment. Kranz’s script smartly focuses on them rather than trying to make specific pronouncements about how this kind of tragedy could be avoided in the future. If films are in part useful for workshopping different situations we might encounter in life, Mass establishes itself as one of the most formidable dramas released about this particular, unshakable hypothetical felt by American parents.

Mass will have an encore in-person screening at the 2021 Heartland International Film Festival at 5 p.m. EDT Wednesday, Oct. 13 at the Kan-Kan Cinema and Brasserie.

Purchase tickets here

Mass also opens in regular theatrical release on Friday, Oct. 22.