Incomplete Information as Suspense.
If someone asks you the type of relationship between you and someone and you voiced without saying anything negative about such and the inquirer paused, pondered and finally voiced,
“Hmmm, be very careful … !”
Now if you meet the person (he or she) hours or days later the information will re-echo in your mind! But there’s vacancy, suspense and you naturally crave to know what’s up!
If you’d lived, worked … with the person maybe co-worker, co-tenant, classmate, acquaintance … you might have an idea of what the person could do or say but you can’t categorically fix what the person is up to?