what is a doppelganger??
The wiki write-up is actually pretty good: https://en.wikipedia.org/wiki/Doppelg%C3%A4nger
In this case a doppelganger is a look alike. It has a more sinister meaning looking at it’s origin.
It’s been said that if you meet your doppelganger, you don’t have much time left to live.
Some have posited that God has a Plan for everybody, and everybody has a date with Mr. Death. If your appointment occurs in a fashion such that events which you were supposed to influence fail to happen by your own volition or by no fault of your own, the doppelganger arises to implement them prior to your death.