it doesn't get any more "undercover" than this:
Titanic: Adventure Out of Time - you can call it "sci-fi-historical" undercover
The Last Express - historical undercover by "accident"?
Secret Mission - agent on a.. secret mission?
In Cold Blood -
CIA has requested assistance of British MI6 to send an agent into Volgia, a former Soviet republic under control of General Nagarov. You are John Cord, MI6 agent chosen for the assignment.
