Olivia identifies September among many pictures of different Observers. Broyles says that they've been looking at these people for three years; why did he make contact now? Olivia recalls what he said: He'd seen all possible futures, and in every one, she had to die. She thinks it's a warning.
On a Boston street, a teenage girl hears a wobbly hum in her head and begins drawing furiously on her sketchpad. She spots a man, rips out the drawing, and gives it to him. His companion thinks the picture's sick, but he laughs it off. Moments later, a falling I-beam impales him horribly - just like the drawing shows.
Olivia goes to Harvard, where Walter and Peter are working together on the Machine. Lincoln calls her about the impaling. Someone handed the victim a sketch showing his death, as if predicting it. No, the person wasn't bald; she was a teenage girl.
The girl, Emily, lives with her parents and brother. While drawing an idyllic picture of a bench beside a tree-shaded lakeshore, she hears that same hum. She asks her dad if he's tired of moving around so much, because of her, then wonders why God made her like this. He says that God has a purpose for everyone, even if we can't understand it.
Olivia tells Broyles that she never believed in fate, but given this case, she's not sure. She's taking migraine pills when Lincoln says they have a lead on the girl from a surveillance tape.
Meanwhile, Emily hears the hum while on the bus and starts sketching. She spots a man near the back but doesn't notice him getting off. She can't give him the drawing.
Lincoln and Olivia find Emily's family and run into the girl outside her building. She explains that, whenever she's around someone who's going to die, she sees it in her head but can't do anything about it. Lincoln spots the folded paper Emily's holding. Has she seen something else? Maybe they can stop it. Then Emily's dad, Jim, angrily tells the agents that, no matter where they go, people find Emily. They want to grab her - and take her to Massive Dynamic. Suppressing surprise, Olivia gives Jim her card.
Olivia confronts Nina, who defensively says MD did approach the family, in Baltimore. They just wanted to catalog Emily's fascinating precog abilities. Olivia can't believe that Nina would want to examine Emily, after seeing the damage done to Olivia as a child. It's abuse. Nina seems stung, but they're interrupted by Olivia's phone.
It's Emily, calling without her dad's knowledge from a lakeside, like in her drawing. Olivia meets her and sees that the sketch from the bus shows many bodies, including the man Emily wanted to give the picture to.
Walter examines Emily. The theta-one waves in her occipital lobe are remarkably active, and her brain is drawing elevated levels of oxygen and blood. He and William Bell believed some traumatic future events echo backward in time, like vibrations. Perhaps Emily's brain is sensitive to that. She explains the images are like dreams: Vivid at first, but they fade. That's why she draws them. Peter asks why she warns people, if they can't do anything? Emily tearfully says that maybe, if people knew, they could say goodbye to someone, or just do one good thing.
The agents called Jim, who arrives and agrees to let Emily help. Astrid matches Emily's drawing to a bus-pass photo of one Albert Duncan, and Peter gets Walter to hypnotize Emily. She sees bodies flying everywhere, then describes a sign, in Latin, and Duncan holding a weird-looking radio. Peter realizes Duncan's in a courthouse - with a bomb.
They track Duncan, who recently lost custody of his kids, to the Allston Courthouse. As police and FBI start evacuating, Duncan looks for the judge in his divorce. Given the destruction Emily saw, the bomb must be huge. Lincoln, Peter, and the bomb squad head to the underground garage, where Lincoln finds the bomb.
Remembering the bald man's warning, Broyles tries to get Olivia to leave, but she refuses. They block the detonator's signal by turning all their radios to the same frequency, 432.5 megahertz. But Duncan also has a bomb strapped on! He tells Olivia that this isn't his fault; it's because of the judge. This is how it has to end. Olivia says nothing HAS to happen. It's up to him. He tearfully surrenders.
Later, Olivia and Lincoln find Emily at the lakeside, obviously ill. She's added to her drawing: Now she's on the bench beside a man. Olivia says they saved the people. Jim arrives, sees Emily's sketch - and realizes what it means. He sits next to his daughter. She hears the hum, and blood trickles from her nose. The overload of electrical activity in her brain has killed her.
Later, Peter notices Olivia's photo of September and explains about the Observers. She asks, could one ever be wrong about the future? Peter says no, they've already experienced it. Has she had contact with one? She says no.
Nina visits Olivia. Both regret their earlier encounter. Olivia thought that she was going to die today, without Nina knowing how she felt. You're the closest thing I have to a mother, Olivia says, and I love you. Nina's touched. When Olivia mentions her migraines, Nina insists on making her soup. Tomorrow she'll send Olivia a new drug from Massive Dynamic. It's remarkable. Olivia smiles.