Mario Petrucci's poem "Heavy Water" serves as the inspiration for director David Bickerstaff's documentary exploring the devastating aftermath of the Chernobyl Nuclear Power Plant explosion. As a gigantic radioactive cloud spreads out from northern Ukraine into Belarus, unassuming citizens gather for May Day celebrations, and the townspeople of Pripyat become mesmerized by inferno that rages on the horizon. It would only be 72 hours before the radioactive dust settled over a massive parcel of land, creating a contaminated zone that destroyed all life. In this film, we hear from the very men and women who risked their lives to help contain the disaster on that fateful day, and discover the truth about the lasting effects that it had on their friends, neighbors, and loved ones.