General:
* Suspicious: They have a look in their eye, a slight tilt of their head, that says they're not buying what they're being told.
* Wary: They're cautious and on edge, their body language tight and reserved.
* Intrigued: They're drawn to the situation, their curiosity piqued by the air of mystery.
* Apprehensive: Their face is drawn with worry, a sense of unease hanging in the air.
* Perplexed: They're confused and bewildered, trying to piece together the puzzle.
* Concerned: Their eyes are filled with worry, their tone hushed and empathetic.
More specific:
* A knowing look: They give you a look that speaks volumes, suggesting they understand the true nature of the situation.
* A raised eyebrow: A subtle gesture that conveys skepticism and doubt.
* A sigh of resignation: They know they can't ignore the problem any longer.
* A grimace of disgust: They're repulsed by what they know is happening.
* A quiet determination: They're not giving up, they're ready to face the truth.
Figurative:
* Their antennae were twitching: They were picking up on subtle clues and sensing something was amiss.
* Their gut was churning: They had a deep, primal sense that something wasn't right.
* Their intuition was screaming at them: They had a strong inner feeling that something was wrong, even if they couldn't explain it.
The best way to describe someone who knows something is wrong depends on the specific situation and the character you're trying to portray. Choose the phrase that best reflects their personality and the level of their awareness.