The RMS Queen Mary is in the business of bringing home war brides after WWII. Beaumont McSwain, former RAF fighter pilot injured in a mission, is onboard the ship as the legal officer. It's his last crossing before mustering out and all he wants is to go home to the family mansion in New Orleans.
Zoe Langlois, a member of the French Resistance during the war, fakes a marriage license and boards the ship for passage to America to find the surviving members of her family- the ones who got out before the German occupation of Paris.
Someone onboard has plans for the French passengers which doesn't include safe entry to the United States. Those ladies begin to die in violent circumstances with notes accusing them of war crimes found nearby. Zoe fears she's on the short list of potential victims and is desperate to hide her true identity.