For many Americans, the story of the Japanese fishing crew that was exposed to a U.S. hydrogen bomb test in the Pacific Ocean 65 years ago may be a footnote in history easy to overlook.

But Keith Reimink, a 40-year-old American documentary filmmaker, reacted differently when, in 2014, he came across a tiny paragraph mentioning the incident in a nearly 500-page book criticizing the U.S. management of nuclear weapons.

Little was mentioned except for the fact that the 23 Japanese men aboard the tuna fishing vessel Fukuryu Maru No. 5 suffered radiation poisoning and that one of them died. But the Pittsburgh-based movie director was intrigued, and by the end of the year, his group was already in Japan to film interviews with three of the former fishermen.