It is always good to look back and see a movie from yesteryear that brought us the necessary film techniques for today's movies to be so successful. As is the case of some films that echoed in the film industry at the hands of the genius Alfred Hitchcock.
Chained is a spy stories, where the main character (Ingrid Bergman) is a spy who tries to unmask some men who worked with her father, a Nazi spy, in a crime of treason against the United States after World War II. But something unexpected happens and she falls in love with Devlin (Cary Grant) a police officer investigating the case.
Sebastian marries Alicia (Ingrid Bergman) and is the main suspect in this story because it turns out to be another Nazi spy who collaborated with the girl's father. When he finds out that he has married a spy who intends to bring him to justice, he tells his mother and the two devise a plan to poison her so that she dies slowly.
In the end Devlin rescues Alicia and Sebastian (who still loves her) lets her go so that his partners do not find out that he had married a spy but it is too late and they realize.
A curiosity of the film is that the transition of the shackled that is, it is a gradual effect where the image of plane A disappears at the same time that the image of plane B appears, having a moment in which plane A and B overlap. And its most significant utility is to create a temporal ellipsis, that is, to show a not very long period of time.