<-- Previous EpisodeNext Episode -->
Fringe: Through the Looking Glass and What Walter Found There
Walter discovers that one of his tapes holds the key to defeating the Observers. To obtain it, he must travel to an abandoned apartment building where time and space are compressed. Peter, Olivia, and Astrid follow, and Peter discovers that he may be able to fight the Observers directly.
Walter: This is very important. Do not, under any circumstances... is that raspberry filling?
Olivia: Is that Donald... Walter?
Walter: No, that's collateral damage.
Walter: Don't you see? I'm not safe. It's my mind. Ever since the pieces of my brain were reimplanted, it's been changing me. Back into the man I was before, bit by bit. I'm losing myself, Pete. I'm losing the man that you helped me become.
Peter: Listen to me. I'm not going to let that happen. We need you. You are our only hope to defeat the Observers. And I'm going to be here with you every step of the way.
Walter: Please, son... don't let me go.
Peter: I won't, Dad.