suspicion breeds suspicion; once you suspect, everything looks suspicious
A yojijukugo abbreviation of the longer phrase 疑心暗鬼を生ず. Used to describe a state where suspicion makes one see threats or deceit everywhere, even in innocent things.
See also: 疑心暗鬼を生ず
Since he started suspecting an affair, he's become suspicious of even his wife's innocent actions.
Once you suspect wrongdoing, suspicion spreads throughout the entire organization.