10/26 - Kaitlin comes back to Newport. She looks and acts so different that Ryan doesn't recognize her when she drops by the Cohens after being told her mother's mail was forwarded there. It seems that her mother forgot to tell her that they had moved. Later, Marissa gets angry at her sister for her bad behavior; Kaitlin is angry at Marissa for not calling her every time something major happened to the Coopers. Ryan tries to have both sisters reconnect. Source: SpoilerFix.com
10/01 - Kaitlin may reappear sometime between episode 3.12 and 3.15. We should see what she's been up to and it doesn't seem like she's been a nice little girl. Source: SpoilerFix.com

Yep, I foresee lots of trouble where Caitlin is concerned. I hope they're not planning on some kind of statutory rape storyline with her and Johnny...