bolt from the blue
Something sudden and unexpected; an event that you did not see coming; a great and usually unpleasant surprise; shock.
Что-то неожиданное; непредвиденное событие; шок.
We had been sure she was in Chicago, so her sudden appearance was a bolt from the blue.
His decision to resign was a bolt from the blue.
The chairman's resignation came as a bolt from the blue!
Отставка председателя была громом среди ясного неба.