How do you find an enemy who is hidden right before your eyes?

Other lines from this film

• The secret is out.
• Trust no one. Suspect everyone.
• The enemy is within.
• At the height of the Cold War, only a master spy could be trusted to expose one of their own.

Similar meaning

Lines whose meaning sits closest, by embedding similarity.

Same sentence pattern

Shape: how do you … an … who is … … before your …