the handwriting on the wall

Also, writing on the wall. A warning or presentiment of danger, as in The company was losing money, and seeing the handwriting on the wall, she started to look for another job. This expression comes from the Bible (Daniel 5:5-31), in which the prophet interprets some mysterious writing that a disembodied hand has inscribed on the palace wall, telling King Belshazzar that he will be overthrown.

A phrase recalling an Old Testament story about Daniel. While a king was holding the Jews captive in the foreign land of Babylon, in the sixth century b.c., a mysterious hand appeared, writing on the wall of the king's palace. The king called upon Daniel, who interpreted it to mean that God intended the king and his kingdom to fall. The king was slain that night.