There clearly seems to be a connection between little girls and horror films. Paranormal Activity 3 seems to try and ride on the same connection as it revolves around two girls playing spirit games and getting more than they bargained for. It reminds one distinctly of Samara from The Ring, and many other 'spirit game' horror films.
The story is narrated in the present by the girls who've grown up and claim to have no memory of the past. What we do see is video recordings of what happened (true to Paranormal Activity style) when the two were small.
Promising to reveal the secret behind the 'activity', the film does successfully give you a peek into the scary moments that await you. Will it really live up to the expectations, however, remains to be seen.
After watching the trailer, you may think twice before standing in front of the mirror at night and whatever you do, don't turn off the lights!