I’ve just added a few stills from The Happy Sad to the gallery. You can check out previews below. Also, Michael Ausiello had this to say in response to a question about Ari and Fringe:

Question: I’m sad Kirk Acevedo is leaving Fringe, but what I really want to know is if Ari Graynor is coming back for season 2. She and the niece added something special to the show, and showed us a different side of Olivia. –Tim
Ausiello: Yes, Graynor’s Rachel returns in the season premiere. Her involvement beyond that is TBD.