A killer targeting love is investigated by the Fringe team on this return episode.
Olivia confides in Nina her feelings for Peter, and Nina cannot believe the cost she is paying for her new memories.
Olivia asks Walter to put her back to the way she was, so she can stop feeling for Peter.
Olivia decides to let the other Olivia's feelings take over.
Peter activates a beacon, reactivating September.
September tells Peter he has always been where he belongs, and Olivia is his Olivia.
Peter and Olivia embrace.