Walter, Peter and others in “Unfinished Business”

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.

I won't, Dad.