At the local psychiatric hospital, Ray McBreen is talking to his wife, Lilly, who is muttering over her piano. Dr. Lucassi and Nurse Gail are working with two comatose patients, Howard Sperry and William. The other nurse, Howard, goes out to the kitchen with Gail. They hear a crash and run to investigate, and find Lucassi standing over a spilled tray of medicine. He tosses an intern, Morgan, into a wall.
Nathan and Audrey discuss her first day working with the Haven police, and that she's staying so she can determine if the woman in the photo is her mother. Audrey admits that she thought her first few cases would be more troubling. They're interrupted when Nathan gets a call about an incident at the psychiatric facility. When they arrive, they discover that the doctors are the ones who are on a rampage. They approach Lucassi and, when it's clear he won't respond to reason, Audrey doses him with ether and knocks him out.
As the staff recover, Audrey determines that the three patients in the room with Lucassi when he went insane have escaped. As they go, Nathan figures that Audrey likes the weirdness and is looking for something to justify her presence. They get word of two of the patients stealing clothing and go to the house. They find the patients, William and Howard, playing peacefully with the children.
Ray returns home and finds his wife Lilly checking the food. She seems to be perfectly normal with no signs of the mental problems that forced him to have her taken to the psychiatric facility. They embrace, Ray in tears with relief and shock.
Audrey and Nathan return the two male patients to the facility, and Howard starts talking about flowers. Both of them suddenly go comatose while Lucassi recovers as he's taken out on a stretcher. He volunteers to help and Audrey has him unstrapped so that he can check on his patients. He warns that the two patients were catatonics, and that Lilly is dangerously violent.
Lucassi goes with Nathan and Audrey to Lilly's house and they find Ray returning with food. He thanks Lucassi for his help, but they discover that Lilly has gone berserk and fled. The doctor explains that Lilly was a musician with an obsessive disorder, and Ray figures that Lilly will seek out a piano. First they test Lucassi's medicine to see if that's what caused the strange behavior. Nathan talks to Ray, who explains that Lilly loved writing music, and a record executive heard one of her songs. Ray talked her into going to her favorite composing place, but he drove off the road into a river. Lilly was submerged for eight minutes and only avoided brain death because of the cold, and Ray blames himself.
As Lucassi recreates the exact dosage, he explains to Audrey about how he's trying to cure Alzheimer's. He talks about the soul, much to Audrey's surprise, and admits that his approach is highly unlikely to succeed. Lucassi gets her out of the lab on a pretense and then locks the door behind her and tries to determine if he has a cure by spilling the drugs again. However, this time nothing happens.
As Nathan and Ray search for Lilly, they spot Duke walking by with a mounted fish. Duke insists that he bought it, but Nathan doesn't believe it. The smuggler hints that Audrey doesn't know everything about Nathan, including the fact he's not a real boy. Before Nathan can pursue the matter, Ray calls him into the nearby bar where he's found Lilly.
At the police station, Audrey and Lucassi review the video footage from the psychiatric facility. They notice William nearby and realize that he was already cured before Lucassi spilled the medicine. Audrey calls Nathan, who tells her that they've found Lilly trying to play the piano without success. Ray tries to get through to his wife, playing the piano with her. As Audrey and Lucassi arrive, they discover that the bar customers are going on an insane rampage. They go inside and find Nathan holding an open flame to his arm. Audrey realize that he's been affected by the same plague of insanity. He storms out past Audrey and walks away.
As the police mobilize to confine the newly-insane townsfolk, Lucassi suggests that the common factor is Lilly. Before Audrey can pursue the matter, she gets word that Nathan is down at the marina.
Duke is working when Nathan arrives and asks him what it is like to be able to few things. He attacks Duke, blaming him for all the things he's done to Nathan. Nathan starts strangling him and Audrey arrives and tasers him unconscious. She tells Duke to keep him there and he reluctantly agrees. She then calls Lucassi and asks him if Lilly was playing the piano when things happened. Lucassi confirms that she was and Audrey goes back to the facility to take a look at Lilly's room.
Duke chains Nathan up. When he recovers consciousness, Nathan rants and accuses Duke of being a parasite who uses people. He wonders if Duke is going to use Audrey, and Duke punches him. Undeterred, Nathan insists that Duke can't hurt him, and Duke walks away.
Audrey finds a photo of Lilly and Ray at Ray's boat, the Caprice, and figures that they're hiding out there. However, the boat isn't at the marina. Lucassi explains that Ray's grandfather abandoned the boat when the McBreen family washed up in Haven. Duke calls Audrey to tell her that he's done playing host to Nathan. Nathan regains his senses and Audrey comes to get him. She explains her theory that Lilly's music is causing insanity, but he isn't convinced. He notes that Ray was sitting with Lilly playing the piano with her when the outburst of insanity started.
At a boatyard, Ray is preparing to leave with Lilly, who is sane again. She realizes that he caused the insanity and insists that he can't do it.
Audrey remembers that Ray was at the facility when Lucassi went insane. They figure that now he knows what he's doing.
Ray insists that he doesn't want to hurt people, but unpacks musical instruments when she isn't looking.
Duke overhears Nathan and Audrey talking, and offers to take them to the boatyard. When Duke is reluctant to volunteer the information unless he comes with them, Audrey reluctantly gives in.
Ray discovers that Lilly is acting irrationally again. He starts playing his guitar to use his ability to cure her. Lucassi, trying to find the boat, goes insane while Lilly recovers. The doctor climbs into the boat and attacks Ray.
Nathan and Audrey arrive with Duke, and Audrey tells him to stay at the truck. She realizes that the periods of insanity vary, and wonders why Nathan recovered more quickly. Lilly runs up to them and they capture her, and explain that Lucassi took Ray captive and drove back to the facility. They drive there with Duke and Lilly, and have Duke watch her while they go inside to find the doctor. Audrey wonders if Lucassi can actually cure his patients using Ray's ability. When they get inside, they discover that Lucassi has strapped Ray down and is preparing to remove his brain. They burst in and try to calm the crazed doctor. Audrey manages to get close enough to grab the electric paddles and shock him unconscious. She's realized that Nathan recovered when he was shocked by her taser, and she figures the same approach would have worked on Lucassi.
Lilly comes in and warns her husband that she's starting to lose her grip on sanity again. When he tries to find a musical instrument, Lilly insists that it's not worth the harm to others. Ray doesn't want to lose her, but Lilly makes him promise not to cure her again. She starts singing to him but then goes insane.
Back at the psychiatric facility, Ray explains that the first time he played in years was at the facility on the day that the insanity first struck. He explains that his grandfather owned the boat, and had warned Ray to stay away from music. Ray figures that his grandfather knew about his gift. Audrey suggests that they let Ray and Lilly sail away on their boat. Alone, Ray can keep his wife sane.
Lilly is in her room when Ray arrives and plays his harmonica. Once she recovers, they get her out and take her, Howard, and William with them. As they pack to leave, Ray promises that one day they will return once he's worked out a way to maintain their sanity and not affect others. Howard notes that Audrey looks just like a woman he used to sell flowers to years ago, but doesn't remember names, only the flowers they purchased. He confirms it was in 1983 and remembers that the woman's name was Lucy.
Later, Duke asks Audrey not to tell anyone that he helped out. He realizes that the troubles are back and Audrey agrees. Audrey then tells Nathan what she's discovered about Lucy, and Nathan is called on to look for the three missing patients.