Most of the action takes place in a bus station, with different stories revolving around the various passengers like a Marine, played by Richard Travis, and Julie Bishop, a traveler who will inadvertently carry the bomb on board the bus. The Japanese spies responsible for the bomb have placed it there with the timer set to detonate when the bus stops at an oil field, and the explosion will act as a beacon to show a submarine crew where to bomb.
Also in the cast was twenty-year-old Eleanor Parker, who had been approached by Warner Bros. while performing at the famed Pasadena Playhouse. It was not the first time a studio had tried to sign her; she had been wooed by 20th Century-Fox while still in high school, but she preferred to finish her education, first. When Warners came calling, she asked them to wait until she finished her first year at the Playhouse. When the year was up, Parker phoned the studio in June, 1941 and was signed. Busses Roar has been noted as Parker's feature film debut, but that is a technicality. She had already filmed scenes for They Died with Their Boots On (1941), but the film ran too long and those scenes were cut. Because the studio was paying Parker without a project lined up, they made her act in screen tests for other actors until Busses Roar was ready to go into production.
The film went through several working titles, including Busses Roar at Midnight, Busses Roar at Night and screenwriter Anthony Coldeway's original story, The Busses Roar, before the final release title was decided. It was directed by D. Ross Lederman, with a script by Coldeway and George Bilson, and was decidedly a "B" picture, playing at the bottom of the bill with films like The Major and the Minor (1942) among others, after it premiered at The Palace on September 24, 1942.
Most of the critics praised the action and the fast pace of the film, but "T.V.P.," writing for The New York Times wrote a scathing review in which he declared that the "[s]uspense hinges on whether the saboteur will succeed in completing his evil deed, but he is such a bungling fellow that there is no doubt after the second reel about the outcome of it all. The Warners should have thought twice before letting this number past the studio gates."
Some of the newspapers were careful to note in their reviews that "Chester Gan, Chinese actor, plays a Japanese part." Busses Roar was shot during the time in which Japanese nationals and Japanese-Americans were rounded up and forced into relocation camps. As a result, there were no Japanese actors left in Hollywood, although there were many films featuring Japanese characters during the war. Their parts would be played by Chinese-American and other Asian actors.
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Hanson, Patricia King and Junkleberger, Amy AFI: American Film Institute Catalog of Motion Pictures, Vol 1-2
The Internet Movie Database
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T.V.P. "At the Palace: Busses Roar" The New York Times 25 Sep 42
"'Busses Roar' Drama on New Park Bill" Youngstown Vindicator 31 Oct 42