Charade (1963)

In this Hitchcock-like thriller (similar to To Catch a Thief (1955) and North by Northwest (1959)) and mystery-romance by director Stanley Donen - a tale about the search for missing and stolen gold treasure worth $250,000 by five survivors of WWII who were in the Office of Strategic Services (OSS) together, and were now threatening the newly-widowed and estranged wife of one of the accomplices:

• in the opening, the tongue-in-cheek sequence set at a swanky ski resort at Mont d’ Arbois in Megeve, Switzerland, in which a gun was pointed at lovely Regina ("Reggie") Lampert (Audrey Hepburn) on her holiday - held in the grip of the young son of her friend - it was a water pistol!
• upon her return to Paris, Reggie's shock to find that her husband Charles, who she was planning to divorce, had been brutally murdered during her absence, by being thrown from a train; she was given his possessions in a Lufthansa travel bag: a letter addressed to her, a ticket to Venezuela, passports in multiple names and other items
• the scene of the funeral of Reggie's murdered husband Charles, when three strange men (three of the accomplices) - later identified as Tex Panthollow (James Coburn), Herman Scobie (George Kennedy), and Leopold W. Gideon (Ned Glass), sternly paid their respects by staring into the casket to assure themselves that the man was dead
• Reggie's reaction to CIA administrator-agent Mr. Hamilton Bartholomew's (Walter Matthau) warning at the American Embassy that the three men were probably coming after her: ("If you're trying to frighten me, you're doing a first-rate job!")
• the often witty (and goofy) dialogues between "Reggie" and charming American stranger 'Peter Joshua' (Cary Grant), such as: (Reggie: "Do you know what's wrong with you?" Peter: "No, what?" Reggie: "Absolutely nothing")
• the violent fight scene on a slippery Paris rooftop (with a backdrop of neon lights) between Peter and hook-handed Herman Scobie
• the revelation to accomplice Tex Panthollow who suddenly realized (in a creatively-filmed sequence) at a Thursday outdoor stamp fair market that Charles must have bought expensive rare stamps there and placed them on an envelope to hide his $250,000 worth of treasure

Tex's Sudden Revelation	Valuable Stamps

• Reggie's visit to a kindly rare stamp dealer Mr. Felix (Paul Bonifas) with a large magnifying glass, who revealed that the stamps torn off an envelope (addressed to her from her husband) were extremely valuable
• the concluding tense chase through the streets of Paris and onto Metro cars and subway stations - when Reggie was pursued by the enigmatic and seemingly-untrustworthy thief 'Adam Canfield' (one of 'Peter Joshua's' four aliases or identities; he also falsely claimed he was Carson Dyle's brother, Alexander)
• the scene of the anxiety-producing, chase and tense stand-off between 'Adam' and gun-wielding 'Mr. Bartholomew' - when Reggie had to decide who was telling the truth: (Adam: "Reggie, stop! That man is Carson Dyle...I tell you, he's Carson Dyle....If you take him those stamps, he'll kill you, too..." Bartholomew: "Mrs. Lampert, he wants the money for himself. That's all he's ever wanted" Reggie: "He's with the CIA. I saw him at the embassy" Adam: "I tell you, he's Carson Dyle"); she became exasperated with both of them: "Oh, I don't know who anybody is"; they continued: (Adam: "Reggie, I beg you. Just trust me once more" Reggie: "Why should I?" Adam: "I can't think of a reason in the world why you should")
• the final plot twist revelation came to light when Bartholomew admitted that he was actually one of the accomplices (a fifth individual named Carson Dyle, who was thought to have been fatally wounded in a German ambush) - and that he had vengefully murdered the others: ("...it takes a lot of bullets to kill me. They left me there with five of them in my legs and my stomach. Mrs. Lampert, they knew I was still alive, but they left me there. I spent 10 months in a German prison camp with nothing to stop the pain. They left me there, Mrs. Lampert. They deserved to die...You've got the money now. It belongs to me. Mrs. Lampert, they knew I was still alive, but they left me there. That's why I had to kill them, all four of them. Please believe me, Mrs. Lampert. I'll kill you, too. It won't make any difference. It's no use. You're running out of time. I've come too far to turn back. I swear, I'll kill you")
• the confrontation continued into an empty theatre, where 'Adam' calculated where Bartholomew/Dyle was standing above him on the stage and was threatening to kill Reggie: ("The game is over, Mrs. Lampert"); 'Adam' pulled a lever to release the A-4 trap door, that propelled the killer downward to his death; after being saved, Reggie apologized to 'Adam': "I'm sorry I thought you were the murderer, but how was I to know he was as big a liar as you are?" - he quipped: "Is that all the gratitude I get for saving your hide?"
• the denouement the next morning, when "Adam" and Reggie joined together and visited the Treasury Department, but he insisted that she enter alone into the second floor office; to her shock and amazement, she found him in an inner office, sitting at a desk - he was revealed to be a good guy - none other than undercover agent Mr. Brian Cruikshank
• the closing discussion between Reggie and Cruikshank about marriage was interspersed with his demands for the hidden fortune (stamps), and her continuing torment and confusion about his real name and identity:
  - Reggie: "...Marriage license! Did you say marriage license?"
  - Cruikshank: "Now don't change the subject. Just give me the stamps."
  - Reggie: "Oh, I love you, Adam... Alex... Peter... Brian... (his identities were seen in split-screen) Whatever your name is. Oh, I love you. I hope we have a lot of boys and we can name them all after you."
  - Cruikshank: "Well, before we start that, may I have the stamps?"