the writing is on the wall | see the ˌwriting on the ˈwall ( NAmE also the ˌhandwriting on the ˈwall )
( saying ) used when you are describing a situation in which there are signs that sth is going to have problems or that it is going to be a failure :
It is amazing that not one of them saw the writing on the wall.
ORIGIN: From the Bible story in which strange writing appeared on a wall during a feast given by King Belshazzar, predicting Belshazzar's death and the fall of his city.