Because her father was convicted of being a Nazi spy, Alicia Huberman (Ingrid Bergman) is recruited by U.S. Government agent T.R. Devlin (Cary Grant) to go undercover and spy on wealthy German businessman Alexander Sebastian (Claude Rains) and his circle of German scientists operating out of Rio de Janeiro. Alicia has a reputation for being wild and promiscuous, and Devlin expects her to stop at nothing to get the information he needs... what is buried in the locked wine cellar.

No. Notorious is based on a short story, The Song of the Dragon by American writer John Taintor Foote (1881-1950), that had appeared as a two-parter in the Saturday Evening Post in 1921. The short story was adapted for the screen by American screenwriter Ben Hecht.

The famous kiss scene between Alicia and Devlin occurs at Alicia's apartment in Rio. It starts on the balcony and moves into the apartment where Dev makes a phone call while the kissing scene continues. The reason that it is "famous" is because it flouted then-current film code regulations that restricted the length of kisses to only a couple of seconds—each kiss stays within the code regulation, but the entire kissing scene is approximately three minutes long.

Pitchblende, a black Uranium ore and a key ingredient in the creation of nuclear weapons.

Devlin doesn't believe that Alicia was suffering from a hangover the last time they met; instead, he thinks she may have been very ill. He visits the Sebastian mansion, hoping to have a chance to square things and say goodbye to Alicia before he is transferred to Spain and a new agent is assigned as her contact. He finds Alicia so weak that she can't get out of bed, and she tells him that Alex and his mother are on to her and that they've been poisoning her. Realizing that he must get Alicia to a hosital immediately, he gets her out of bed and slowly helps her down the stairs. Alex and his mother try to stop him, but their Nazi confederates (who don't know that Alex is trying to kill his wife because she is an American agent) begin to ask questions. Devlin reminds Alex of what his "friends" did to Emil (killed him) and that they will do the same to him when they realize that Alex has compromised them. Alex plays along with Alicia's "collapse" and the need to get her to a hospital, intending to get in the car with them and escape. However, when Devlin gets Alicia into the car, he locks all the doors and says, "No room, Sebastian." In the final scene, his two Nazi "friends" learn that there is no telephone in Alicia's room by which they could have called the hospital. They call Alex back into the house, saying that they wish to "talk" to him. Alex obediently goes inside, and the door closes behind him.

Alfred Hitchcock did a cameo in most of his movies from The Lodger: A Story of the London Fog (1927) onwards. His cameo in Notorious appears about 60 minutes into the movie. In Notorious, he is seen quickly downing a glass of champagne in the party scene.