The Bramble Bush
From Alfred Hitchcock Wiki
Introduction
An adaptation of a 1948 novel by David Duncan about a disaffected Communist agitator on the run from the police, forced to adopt the identity of a murder suspect. The story would be adapted to take place in Mexico and San Francisco.
The politics and high budget made it a difficult project. Ultimately, Hitchcock did not feel that any of the scripts lifted the movie beyond an ordinary chase story, and he got permission to kill the project and move on to "Dial M for Murder".
The theme of the hero assuming a dangerous new identity would become "North by Northwest". Michaelangelo Antonioni's 1975 film "The Passenger" tells a similar story, but is not based on Duncan's book.