Ruthless spies kill an American scientist in a failed attempt to steal the secret formula for a deadly poison. The only other person with access to the process is the chemist's lab assistant, Nadine Nicolas, an immigrant with dreams of becoming a U.S. citizen. Falsely accused of being part of the spy ring, Nadine is imprisoned and misses her last chance to take her citizenship test. Though finally acquitted in a very public trial, she is immediately listed for deportation and put on a train bound for Ellis Island. With the enemy spies still after the formula, the Exile Express is fast becoming a very dangerous ride.

Exile Express is notable for showcasing one of the few Hollywood roles of Anna Sten, a veteran European actress "discovered" by Sam Goldwyn and rushed to the States to be the next Garbo or Dietrich, both of whom she resembles. Alan Marshal, suitably suave as Sten's love interest, is perhaps most notoriously known for literally dying onstage in 1961 while performing with Mae West's oft-banned play, "Sextet." Several consummate comic actors lighten Exile Express with great comedic performances.