hmm. Considering that Crono is not maguel from chrono cross, I'm thinking about something i had in mind for my CT:ToF story.
Crono and Marle are with there 3 year old son, (who's name is Shinrin, yeah i know that it's based on my name, but Shinrin has been in plan as Crono's son for nearly 6 years), now at this time this guy and this young girl was visiting them from the future about some sort of wierd happenings in the year 1987, the girl is the same age as Shinrin. Suddenly guards come in and announce that Porre is attacking the kingdom. the guy tell Crono they must leave now and hands the girl, Elizabeth to Marle, Crono tells Marle to think of a plan to retake the kingdom and then opens up a secret passage for her, Shinrin and Elizabeth to go, after they enter the secret passage, the man opens up a portal and they leave. the porre guards break in to find no one and notices that the secret passage is opened so they go in. Now Marle and the kids are being followed, and the guards catch up. Marle fends the off and continues on, and after walking a little bit more, Elizabeth gets her foot gaught on something and marle tries to help, she tell Shinrin to continue onwards and to be careful. Some more guards catch up with Marle and the girl and Marle gets cut in a face by one of the guards. she knocks them back and tells the girl, that she is sorry and wishes there was another way to get her out Marle flees hurting from her wound and finds Shinrin and they flee to Lucca's house where everyone is and they take refuge in a shelter near by. So, now it focuses on Crono and the Guy and there at a wierd and unusual place, Crono has a familar wind go through him like he did when he fought lavos. The guy tells him about the events of serge even though they was supposed to been erased from everyones minds.... so these two set off in the new dungeon and you're left to wonder what happened. Then maybe show a scene about Kid, Shinrin and the radical dreamers.