Abraham Lincoln will be traveling by rail to his inauguration in Washington and a plot is being hatched to assassinate him as he passes through Baltimore. New York detective John Kennedy (Dick Powell) tries to alert his superiors to the scheme, but his suspicions are dismissed. He decides to quit the force and boards the train to try to thwart the assassins himself. He's unsure of whom he can trust but finds a potential ally in Ginny Beaufort (Paula Raymond), the sister of one of the plotters.