Georg, a German political refugee, narrowly escapes arrest in occupied present-day Paris. He attempts to deliver a letter to a well-known writer named Franz Weidel, only to discover that Weidel has killed himself in a hotel room. He takes Weidel's last manuscript and identity documents, which promise him safe harbor in Mexico. He attempts to flee to Marseille via train with his injured friend, Heinz, but Heinz dies en route. In Marseille, he brings news of Heinz's death to his deaf wife Melissa and son Driss, both of whom are residing in the city illegally. Georg befriends Driss. When Georg attempts to turn in Weidel's papers to the Mexican consul, he is mistaken for Weidel and impersonates him, and is given transit visas for himself and Weidel's wife, Marie. He learns that Marie had left Weidel, but wishes to reunite with him and has been waiting in Marseille so they can flee together. Driss has an asthma attack, and Georg fetches a doctor, Richard, to care for him. Georg meets the doctor's mistress, who he learns is Marie. Richard wishes to flee, but is consumed by guilt over abandoning Marie. However, when Georg offers her a transit visa, Richard goes ahead and tries to board a departing ship, but is forced to give up his spot for French soldiers. Georg and Marie develop a romantic relationship, and he wrestles with whether to tell her the truth about her husband, coming close to doing so, but being unable to do so because she so adamantly believes him to be alive. He learns that Melissa and Driss have fled, and witnesses the suicide of a fellow refugee he had known as an acquaintance. Georg and Marie hail a taxi for the harbor to board their ship, the Montreal, but Georg exits, claiming he has forgotten something. He goes to Richard and sells him his place on the ship. While recounting his story to a bartender, to whom he entrusts Weidel's manuscript, he sees a woman who looks like Marie, but she disappears. He goes to the port to confirm that she boarded, but is told that the Montreal hit a mine and sank with no survivors. He returns to the bar, where he waits for Marie as the French police start sweeping the city to purge it of refugees.
On review aggregator website Rotten Tomatoes, the film has an approval rating of 94% based on 151 reviews. The consensus reads "Transit lives up to its title with a challenging drama that captures characters - and puts the audience - in a state of flux and exerts an unsettling pull."
