The phrase "fateful night" refers to a night that has important or significant consequences. It implies that something important or life-changing will happen on that particular night. Full definition
Every day the people process through the streets, carrying statues of the Holy Family, knocking on doors, and begging, reenacting that fateful night in Bethlehem. (firstthings.com)
I vividly remember that fateful night when Mr. William Kweku Ansah had to be moved from one hospital to the other for medical care. (citifmonline.com)
Finally, one fateful night as she served Meatloaf and mashed potatoes — favorites of mine — she also put a bowl of broccoli on the table. (addapinch.com)