Update,
The storyline will begin just after Porre's destruction of Guardia.(1005 AD)
Marle and Crono will get out, and have to sneak through the ruined city to try and find family and friends.
The whole plot will later be revealed, but this is the sentence I am going on.
Revenge from the one who flows outside of time will lead the rebels into an adventure that goes through the fabric of time.