Spoiler warning: Spoilers for the complete film.
Carter recovers his identity and reaches the escape train with his family, but the bridge explodes before their safety is established. The final cut withholds the outcome of the danger rather than revealing that the mission never happened.
Who is the voice guiding him?
Jung-hee is a fellow spy and the mother of his daughter Yoon Hee. Carter’s memory loss is part of the coercion surrounding a rescue mission intended to secure his family’s freedom.
The search for Ha-na has an additional personal urgency because Yoon Hee is infected. Ha-na’s recovery from the fictional DMZ virus makes her important to the attempt to develop treatment.
That revelation reconnects the directions in Carter’s ear to relationships he could not remember. What first appeared to be purely external control is also a route back to people whose importance has been hidden from him.
A military coup produces another betrayal after Carter fulfills the bargain. He and Jung-hee have to escape with the children and Dr. Jung rather than rely on the authorities to honor the agreement.
Their arrival aboard the train creates a temporary conclusion: the group is together, Carter remembers who he is, and the immediate pursuit appears to be behind them.
The bridge explosion removes only the last of those reassurances. It does not undo the identities and connections the film has already disclosed.
Does everyone die?
The film stops before showing a crash, bodies or a rescue. Death and survival are both possible beyond that cut; neither is confirmed by the completed story.
The person responsible for the explosion is also not definitively identified. A theory involving the forces pursuing Ha-na can explain a motive without becoming an on-screen answer.
The most precise reading separates emotional resolution from physical escape. Carter has recovered the knowledge of whom he is trying to save. The film refuses to guarantee he will be allowed to finish saving them, ending on a renewed threat instead of a completed journey to safety.
Sources: official ending breakdown.