The Fringe team is called to Manhattan after a series of earthquakes hit, which results in a building that seemingly merges with another. While investigating, they find no survivors except for a man that has two sets of arms and legs and a head growing out of his chest!
Olivia and Walter begin to question him, but they can only get a few answers and details about what happened before he dies. Walter ascertains that two building -- one from this universe and one from the alternate universe -- have merged. Olivia is sure that Newton has everything to do with this.
Walter determines that since one building came from the other universe, another building of similar mass from their universe will have to go over there in order to establish balance between the two universes. In order to save the people inside, they need to figure out what building it is before it goes. Walter explains that the building to disappear will have a glimmer that only Olivia will be able to see. She could do it as a child when Walter and Bell would do the Cortexiphan trails on her.
The team goes to Jacksonville because Walter believes that in order to activate Olivia's ability to see the glimmer then she needs to be tested where the original Cortexiphan trials were done. After going under with the drug, Olivia is reminded of what happened to her when she was young. She remembers how frightened she was. Upon waking, she is outraged at Walter but still cannot see the glimmer. It didn't work. Walter explains that Olivia needs to be afraid, like when she was young, in order to be able to see the glimmer. Olivia does not know how to be afraid anymore. She has turned her fear to anger.
Left with unsuccessful results in Jacksonville, they all fly back to Manhattan to see if they can figure out what building will disappear based on mass and weight.
Yet they realize that they will not be able to figure out what building will disappear in time to save those in it. Olivia is distraught that she can't save those lives. In a moment of vulnerability and feeling of utter loss, she is comforted by Peter. Just as they are about to kiss, Olivia realizes that she is afraid. She runs to the NYC skyline and spots the building with the glimmer! The team rushes to find the building and they evacuate it right before it is pulled over to the other side, thus saving everyone's lives.
Later, Olivia and Peter are on their way out the door for drinks. Olivia realizes that Peter is glimmering. He is from the other side! When Peter runs upstairs to get his coat, Walter asks Olivia to keep the secret.