If all stories begin with a disruption of routine, then the "chance encounter" is considered one of those potential disruptions.
A chance encounter occurs when someone from your protagonist's past waltzes back into their world. He has not seen her for years, but, suddenly, there she is.
The chance encounter sets up a fairly deep story, automatically pulling problems from the past into the present. Not only will the reader need to know what happened before (i.e. how they met, some of their experiences together, what drove them apart, etc.), but also how they have changed in the weeks, months, and years it's been since they last saw each other.
This feeds directly into the plot of the narrative, of course, or how the two of them will address and work through their shared history, and the baggage that may come along with this, in order to move forward.
Be Brilliant!
~Katie~
