"Deus Ex Machina" for Misfortune

I'm looking for a word or phrase like "deus ex machina," but to describe misfortune rather than resolution. It needs to communicate that the situation "came from out of nowhere," and/or feels "tacked-on" without any prior build-up.

Any ideas?

Edit: For example:

The ___ in the book really annoyed me. The main character died of an illness at the end, even though nothing of the sort was hinted at in any previous plot arcs.

There is no phrase (that I know of, obviously) that is an exact opposite to the concept of Deus Ex Machina, which is very specific. It doesn't just describe resolution out of nowhere, it describes resolution in the heart of a situation that looks so utterly bleak that there really can be no resolution. I believe Simchona's answer, "sudden tragedy" is the best you will get out of our current language. However it is not an exact opposite since sudden tragedy is free to strike in good, bad, or neutral times, not just good ones as one would expect from the opposite of this phrase.

Since "Deus Ex Machine" literally means "God out of the machine." You might consider using your own psuedo-latin phrase, for example:

 "Nex Ex Machina" (Death out of the machine)
 "Diaboli Ex Machina"  (Satan out of the machine.)

(PS: I know nothing about Latin so I am 100% guessing that I can just grab 'deus' and replace it with other nouns to keep the same meaning!)

To describe a sudden change in a book, you can call it a plot twist. A word that describes more than that given example is surprise:

• something that surprises someone; a completely unexpected occurrence, appearance, or statement: His announcement was a surprise to all.

• a coming upon unexpectedly; detecting in the act; taking unawares.