Deus Ex Machina

Deus ex machina is the Latin phrase originally used to describe an ancient plot device used in Greek and Roman theatre. The phrase is loosely translated as “god from the machine.”

It referred to scenes in which a crane (machine) was used to lower actors playing a god (deus) onto the stage to set things right, often near the end of the play. Its most literal interpretation is when a godlike figure, with all the convenient power that comes with that, arrives to solve the problem.

The literary device of deus ex machina means to solve a seemingly intractable problem in a plot by adding an unexpected character, object, or situation.

With all due respect to the ancient Romans, it's good to avoid using a deus ex machina in your own story though, as readers will feel cheated. Here's a great explanation by the extremely talented, Kathy Bates playing Annie Wilkes in Stephen King's Misery.

If you ever think of taking the easy way out, remember Annie.

But this plot device comes in many disguises. Here are a number of requirements for a sudden plot development to be a deus ex machina:

1. It may be a solution to a problem, but it never make things worse nor does the sudden twist change the understanding of the story.

2. It is external to the characters and their choices throughout the story. 

3. The solution comes from a character with little influence on the plot until that point or by random chance.

One of the most common deus ex machina endings is the "it was all a dream" ending. It hits all the requirements: the crisis is solved through no actions of the protagonists, renders the actions/choices of the protagonists useless, and it comes out of nowhere.

Here are a few more examples:

Near the ending of The Wizard of Oz, after Dorothy is stranded when the hot air balloon takes off without her, the Good Fairy shows up and tells Dorothy she had the power to go home all along.

Why did she send this kid on an unnecessary and dangerous journey that ended up requiring her to kill ANOTHER witch?
Yes, that's right, double homicide. It's not like Dorothy wanted to stay in Munckinville. She wanted to go home right away! Don't get me wrong, I love the movie.  

Also, remember this moment in Jurasic Park? Just when everyone was about to be eaten by the raptors, the T-Rex jumps in and eats the raptor. No one noticed the giant dinosaur inside the lobby?

Annie Wilkes would not be impressed.

Okay, so now that you know what a deus ex machina is, make sure you don't have any in your story.

Happy Writing!