In September 1941, German physicist Werner Heisenberg visited his former mentor, Niels Bohr, at the latter’s home in Copenhagen.

What they discussed and the ramifications of their meeting remains unclear, in part because each gave differing accounts of it after World War II.

Scientists continue to debate what transpired, and Michael Frayn uses that uncertainty as the basis for his 1998 play, “Copenhagen,” which South Bend Civic Theatre premieres Friday as its latest online production.

Set in a place that’s been described as outside time and space, the play reunites the spirits of Bohr, Heisenberg and Bohr’s wife, Margrethe, to finally settle the question of why Heisenberg came to Copenhagen and what happened when he did.

But as the play progresses through a series of re-enactments of their discussion, actress Janine Felder-Kahn says, the mystery about why Heisenberg visited Bohr at that moment only gets deeper and deeper.

“What does Heisenberg want from Bohr?” she says. “Does he want to protect him? Does he want to warn him? Does he want him to forgive him for his acts in helping Germany develop the bomb?”

Ironically, Gary Oesch, who plays Bohr, says, the Nazis’ anti-Semitism and the Holocaust may have done more to undermine Germany’s atomic aspirations than any other factor.

“The interesting thing was that there were several physicists that created the bomb for the Allies in Los Alamos, but the irony, the paradox is that the (German) Jewish physicists, many of them got out because of the Holocaust, ” he says. “It could have gone a whole different way. … To contemplate that Hitler could have had the bomb is frightening.”