The film is notable for its screenplay, especially the repartee between Grant and Hepburn, for having been filmed on location in Paris, for Henry Mancini's score and theme song, and for the animated titles by Maurice Binder. Charade has been referred to as "the best Hitchcock movie that Hitchcock never made."
She is summoned to the U.S. Embassy, where she meets CIA agent Hamilton Bartholomew . He informs her Charles was involved in a theft during World War II. As part of the OSS (the predecessor of the CIA), Charles, "Tex" Panthollow, Herman Scobie, Leopold W. Gideon and Carson Dyle were parachuted behind enemy lines to deliver $250,000 in gold to the French Resistance. Instead, they buried it, but were then ambushed by a German patrol. Dyle was badly wounded and left to die; the rest got away. Charles doublecrossed them, digging up the gold and selling it. He was killed but the money remains missing – and the U.S. government wants it back. Reggie recognizes the oddballs from the funeral in pictures shown to her by Bartholomew. He insists she has the money, even if she doesn't know where it is.
Peter offers to help. Reggie becomes attracted to him, even though he keeps changing his name (simultaneously amusing and confusing her) and unabashedly admits he is after her late husband's money as well. The dead man's partners in crime assume Reggie knows where the money is and demand their share. Unbeknownst to her, Peter is in league with them (under the pseudonym Alexander Dyle, Carson's brother), though none of the men trust each other.
They begin turning up dead — first Scobie is drowned in an overflowing bathtub, then Gideon has his throat slit while sneezing in an elevator. Reggie and Peter go to the location of Charles' last appointment and find an outdoor market. They also spot Tex there. Peter follows him.
It is Tex who finally figures out where the money is hidden. He sees several booths selling stamps. Charles had purchased rare stamps and stuck them on an envelope in plain sight just before he boarded his fateful train ride. The envelope was in his travel bag. Peter realizes the same thing and races Tex back to Reggie's hotel room. They come up empty. The stamps have been cut off the letter.
Reggie had given them to her friend's son for his stamp collection. By chance, she runs into them at the market, only to learn that the little boy has traded them away. Fortunately, the stamp seller is honest. He puts their total value at $250,000 and returns them to Reggie.
Peter tracks her to the rendezvous and Reggie is caught out in the open between the two men. Peter tells her that the man she thought was Bartholomew is really Carson Dyle and that he was the one who killed the others. Another chase ensues, ending with Dyle's death.
Reggie insists on turning the stamps over to the proper authorities. Peter refuses to accompany her inside the embassy office. When she goes in by herself, she is shocked to find Peter (whose real name turns out to be Brian Cruikshank) sitting behind the desk. After proving to her that he is actually the government official responsible for recovered property, he promises to marry her...after she gives him the stamps.
The movie ends with a split-screen grid showing flashback shots of all of Brian's different identities, while Reggie says she hopes that they have lots of boys, so she can name them all after him.