In the short story "Joe Steele", the "Professors' Plot" is an alleged conspiracy of Jewish scientists to deny the United States an atomic bomb during World War II. The plot is "discovered" by President Joe Steele in 1946, when Albert Einstein admits that he and some of his fellow scientists had theorized such a bomb in the early 1940s, but had not shared that theory with Steele for fear that Steele would use such a bomb. Steele, an anti-Semite, orders the deaths of Einstein and several other Jewish scientists, believing that they had all colluded with Einstein.
This "conspiracy" occurs only in the short story. In the novel, a number of physicists are arrested over the years with some being executed while others sent to encampments. However, this was for general "wrecking" rather than for a particular plot. There is also less emphasis on the Jewishness of the accused. Several are already in camps when Joe Steele finds out about a theoretical atomic bomb. Einstein does meet the same fate, however.