When a young woman, Tara, is on a plane with her boyfriend heading home, she suddenly collapses and begins having seizures after exiting the bathroom.
Jacob and Rachel are at his nephew Owen's birthday party. Jacob gives Owen a science book and Rachel gives him a football. During the party, Jacob demonstrates one of the experiments in the book to get Owen interested. Rachel's phone rings and she tells Jacob that they have to go.
Rachel fills Jacob in on their way; people in Oklahoma are dying from a bad case of the bends. They need his help because none of the deceased have been scuba diving or even swimming.
They head to the plane that Tara was on and meet up with a former FBI agent and the school's head of security officer, Blake Miller. They speak to the flight attendant about Tara's behavior prior to her collapse. The flight attendant states that Tara was in the bathroom with a man and his name was Wade Erlan.
They head to the campus where she lived and meet with her sister, who is also a student at the college. They find Tara's sister, Vivian, at Tara' memorial. They ask about Wade and she tells them that Wade is not there. They find Wade in his apartment. While searching his apartment, Rachel finds a bottle of sleeping pills and they question Wade about his and Tara's drug use. Wade gives Jacob some pills telling him that he was told that they make sex better. Jacob does not recognize the pill and Wade states that it is called 'Pearl'.
Jacob and Rachel head over to the medical examiner's office where they discover that Tara had high levels of nitrous oxide in her blood. Jacob surmises that the drug may have caused her body to make bubbles in the blood making it seem like she died from the bends when that wasn't the cause of death.
On campus, Isaac and Lawrence are playing a video game and decide to head out to the track for a run. Isaac begins having difficulty breathing and collapses. Lawrence calls for help and they end up at the hospital. Jacob and Rachel are informed about the incident and head over to the hospital to investigate. Jacob states that Isaac needs to be put into a Barometric Pressure Chamber, but the hospital only has one, and it is broken. Rachel makes a phone call and orders a pressure chamber to be delivered immediately. The request is fulfilled by the United States Coast Guard. Isaac is put into the chamber and he begins to stabilize. Jacob states that this is only a temporary solution. He explains that Isaac's body will continue to produce bubbles so the pressure will have to be adjusted to compensate for this. The human body can only withstand so much pressure which means Hood doesn't have much time to find the cause of the problem and a cure for it.
Jacob receives a drug analysis of Pearl and the main ingredient is sugar. Jacob tells Rachel that this incident seems to be brought on by physical exertion. Jacob questions Isaac about his general health and asks if he had a cold recently. Isaac tells Jacob that he had a flu shot.
Jacob looks at the medical records for all the victims and finds that they all had a flu shot. Jacob heads over to the clinic and collects the remaining doses of the vaccine. The nurse, Dylan, explains that they have treated thousands of people.
On the football field during practice, one of the trainers, Ellis, is speaking with Lawrence and inquires if he wants to have a cortisone shot. Lawrence agrees and Ellis injects him. Dylan is sitting in the stands and Ellis heads over to him. Dylan tells him that everything is going and informs him that the FBI came by the clinic.
Isaac's condition continues to worsen and pretty soon, the chamber will no longer be able to help him. Jacob has tested Isaac's blood and states that there is no flu vaccine. He surmises that whatever Isaac was injected with instead of the vaccine is causing this condition. Jacob meets with the university's biology professor. She recognizes the drug that was identified in Isaac and tells Jacob that it matches a gene therapy drug.
Rachel leaves Jacob at the university and goes off with Blake. Blake flirts with her by telling her that she is a creative, intelligent, and pretty woman. Rachel confesses that with her current assignment it is very hard to have any kind of a normal life. Rachel receives a message from Jacob and they head back to the university. Jacob tells her that he and the professor believe that Isaac was injected with a gene-based drug. This drug is intended to improve athletic performance. Only this drug apparently has a side effect, which results in the death of the test subjects.
Rachel finds out that the nurse, Dylan, from the clinic is majoring in Sports medicine and they figure he must be involved. Jacob heads over to tell Isaac that they have figured out what is wrong with him and are working on how to reverse the damage. Blake and Rachel head out to find Dylan, but he is not at his apartment. They decide to go in and check things out and find numerous newspaper articles about athletes. Not just any athletes, but the athlete siblings of the victims.
Vivian is meeting with Ellis and tells her that she is really angry about her sister's death. Ellis points out that she gave permission for them to test Tara. After Ellis leaves, Vivian decides to report Dylan and Ellis. She composes and sends an e-mail to the authorities. Ellis hacks into her e-mail account and deletes the incriminating message before it can be sent. Vivian leaves her apartment, not realizing that the e-mail was not sent, and commits suicide by diving into an empty swimming pool.
Jacob and Rachel are called to examine Vivian's body and find a picture of Tara in her hand. This leads them to believe that she killed herself because of her guilt over Tara's death. Dylan and Ellis plan on using Vivian's suicide to blame her form everything. All they need is a suicide note, so Ellis hacks into her computer again to write one.
Dylan plans on leaving town only to be caught by the police. Dylan tells them that some of the athletes wanted to find a way to increase their performance without being detected. He admits that Lawrence was not aware that they were giving him the drug. Dylan confesses everything including that he was working with a partner.
Jacob knows they need to create another gene to counter act the one injected. Ellis is also trying to leave by packing up his scooter. The police arrive and Ellis attempts to flee. He drives straight at Rachel, who knocks him off his scooter.
Jacob successfully creates the new gene and wants to head into the chamber to administer it to Isaac. Jacob is cautioned that it is too dangerous to enter the chamber at the current pressure level. Jacob tells the man in charge of the chamber that he is aware of the risks and enters the chamber. Rachel arrives at the football game and explains to Lawrence that he has been injected with the same gene as Isaac. They discuss that he could die if he exerts himself. Rachel's phone rings and Jacob tells her he is with Isaac. Rachel gives the phone to Lawrence and he talks to Isaac telling him that he is on his way over. As Rachel prepares to leave, she tells Blake that if he finds himself with another weird science case to give her a call. Blake responds that it has been a pleasure working with her.