is rotten in Denmark

something is rotten in (the state of) Denmark.

Prov. something suspicious is going on. (From shakespeare's play Hamlet.) Jim: Look, there's a light on in the office, even though it's way past the time everyone should have left. John: Something is rotten in the state of Denmark. Jane: I wonder why Fred is coming in so late every morning. Jane: Something is rotten in Denmark.
See also: rotten