Here's the official episode guide for Fringe season 4 episode 4, "Subject 9". Episode will air on October 14th, 2011.
- Olivia uncovers a dangerous force that may be connected to Walter's past experiments with the drug Cortexiphan.
- Their investigation forces Walter to leave the lab for the first time in years as he and Olivia head to Massive Dynamic in New York to examine old case files.
- Walter struggles with life outside the lab as he comes face-to-face with the demons of his past.