The man behind the mirror

You can just call me twinner.  I come from, what you would call, another dimension.  Most people have alternative versions of themselves living in these dimensions.  We call them twinners.  A small handful of people have figured out a way to travel to these other dimensions, but the catch is is that they actually switch places with their twinner.  I was brought into this dimension around 10 years ago, but never returned.  I don't know why my twinner never came back, but I fear the worst.