a bad state of affairs : MESS
In a sentence:
Harold and Nancy could think of no better way to describe their night than to say that it was a kettle of fish; they walked in the door covered in dirt and cough syrup, and went straight to bed.
In a different sentence:
The monthly newsletter accurately described the team building exercise as a kettle of fish; three VPs were found washed up ashore, the head of HR was found crying in the public restroom, and twelve interns just disappeared.