Captain Colter Stevens (Jake Gyllenhaal) wakes up on a train and discovers that he is in the body of a school teacher named Sean Fentress. He also realizes that he is part of the Source Code, a military experiment that allows him to relive the last eight minutes of another person’s life. His mission is to identify the bomber responsible for the train explosion that killed Sean and prevent a larger terrorist attack in Chicago.
Stevens repeats the eight-minute cycle multiple times, interacting with the passengers and learning more about the situation. He forms a connection with Christina Warren (Michelle Monaghan), a fellow passenger, and becomes determined to save her. Stevens also communicates with Colleen Goodwin (Vera Farmiga), a military officer overseeing the Source Code mission.
As the cycles progress, Stevens discovers that the mission is not about preventing the train explosion; it’s about finding the identity of the bomber to prevent a dirty bomb attack on Chicago. He faces ethical dilemmas as he realizes that the people on the train are already dead in the real world, and he cannot change their fate.
Stevens pieces together clues and uncovers the identity of the bomber, who turns out to be another passenger, Derek Frost. In a tense confrontation, Stevens manages to capture Frost and prevent the Chicago attack. However, Stevens requests one last trip into the Source Code to say goodbye to Christina.
In the final cycle, Stevens confesses his true identity to Christina and tells her to appreciate every moment of her life. He then makes a selfless choice to remain in the Source Code, sacrificing himself to save others. Colleen, moved by Stevens’ sacrifice, allows the program to end, and Stevens’ consciousness is uploaded into a parallel reality where he is at peace.
The film concludes with a reflection on the nature of consciousness, alternate realities, and the impact of our choices on the people around us. “Source Code” is a thought-provoking and emotionally resonant science fiction thriller.