During the filming of "Dr. Strangelove", Kubrick learned that "Fail Safe", a film with a similar theme, was being produced. Although "Fail Safe" was to be an ultrarealistic thriller, Kubrick feared that its plot resemblance would damage his film's box office potential, especially if "Fail Safe" were released first. Indeed, the novel "Fail-Safe" (on which the film of the same name is based) is so similar to "Red Alert" that Kubrick and Peter George sued on charges of copyright infringement. The case was settled out of court. What worried Kubrick most was that "Fail Safe" boasted acclaimed director Sidney Lumet and first-rate dramatic actors Henry Fonda as the American President and Walter Matthau as the advisor to the Pentagon, Professor Groeteschele. Kubrick decided to throw a legal wrench into "Fail Safe"s production gears. Lumet recalled in the documentary "Inside the Making of Dr. Strangelove": "We started casting. Fonda was already set... which of course meant a big commitment in terms of money. I was set, Walter the screenwriter was set... And suddenly, this lawsuit arrived, filed by Stanley Kubrick and Columbia Pictures."