James Mason assumes the role of Diello, the valet to the British Ambassador to Ankara who sold British secrets to the Germans during WWII. The movie is based on actual events.
Making his pitch to Moyzisch, the German Attaché.
Moyzisch securing payment.
Contemplating the combination of the safe.
Diello: I said to myself: If I was an ambitious Attaché to the German government, what would be the combination of my safe?
Moyzisch: How dare you!
Diello: 1-30-33, the year Hitler came to power. I imagine it would open half the safes in Germany, and Hitler's birth date the other half. What an unimaginative lot you are.
Diello confirms the betrayal.
Diello: As for my name....
Moyzisch: You have been assigned the name 'Cicero'.
Diello: Cicero: A man of nobility, eloquence, and dissatisfaction. I like that name.
Diello (to Moyzisch) : ... and please don't have me followed. You Germans have no talent for it. You keep wanting to get ahead of the people you follow.