In the opening scene, Karen is desperately searching for DL57 in order to save Frank's life. She tries to talk to Chris but his fever is so high that he is unresponsive. Meanwhile, Eve figures out that the miracle drug is a mixture of DL57 and the flu virus. Ellen has collapsed and is in bed. Lark is giving Frank a sponge bath. Frank is worried that he is going to die if he does not receive the DL-57. He told Karen that Chris altered the drug. Karen is going to try to recreate the drug.
Mary called to see how Frank was doing. Karen explains that he has a high fever. However, she keeps the full extent of his condition from her. The Greek police have forced Courtney and Joe on to a plane heading back to the United States. Neither wants to leave Greece without Neal. They realize that they need to think fast if they want to be able to save Neal. Eve tries to revive Chris long enough to get information about the drug that is causing this epidemic. One of the doctors wants to give Chris a shot of phenaline. Eve is worried that Chris's heart might not be able to handle the shock of the drug. Eve tries to prevent this from occurring but is unsuccessful. The drug awakens Chris long enough for him to tell Eve that the formula is on the computer in a secret file.
Kevin orders another saline bag for Ellen. She wonders why Kevin nor Eve did not get sick.
Lark feels responsible for keeping Frank's secret. Karen reassures her that it was not her fault. One of the men from disease control entered the room carrying Chris's printouts from the computer. However, they are in code. No one is able to understand the notes and Chris can not be revived. Joe and Courtney escape from the plane.
The man from the disease control center informs Karen that it is now up to her to save the lives of everyone infected by the virus. Mario went into cardiac arrest and becomes the first victim of this illness. Frank went into cardiac arrest as well.
Joe and Courtney catch a glimpse of Neil outside the pastry shop, but they can't approach him because he is accompanied by the Kanelos' body guards. When Courtney becomes quite agitated, Joe calms her down by letting her talk about her reasons for marrying John Kanelos in the first place. She told Joe that her parents raised her to be materialistic and marry a rich man, something she wishes she had never done. Once Courtney is calm, Joe suggests that she call the Kanelos' home and ask to talk to Neil. She call, but Mrs. Kanelos told her that Neil is not with them, that they have accepted the fact that he is not their grandson. Furious, Courtney lies to Mrs. Kanelos, telling her that Neil's leukemia has returned and he has to see his doctors. Even then, Mrs. Kanelos refuses to admit that Neil is with them. After Courtney hangs up, Joe told her that her lie was brilliant. He explains that even the tiniest seed of doubt about Neil's health will make the Kaneloses take him to the doctor, where he and Courtney can try to take the boy back.
At GH, both Kevin and Chris grow sicker by the minute. Karen and Matt press Chris for the code to his DL-56 research notes, and he finally relents, giving Karen the security code for his computer files. Dr. Perry explains to Eve that she and Kevin were slow to succumb to the mutated virus because they had both been exposed to the original strain. Eve realizes that she, like Kevin, will eventually become quite ill.
Karen and Matt successfully concoct a new batch of DL-56, which Matt cultures with live and irradiated strains of the Nepalese flu virus in hopes of discovering how to slow the virus and create a vaccine. While they are working in the lab, Matt notices a tear in Karen's glove.
Gail went to the jail to begin counseling Julie, who responds with suspicion and anger that Kevin has turned her treatment over to Gail. When Gail explains that Kevin is gravely ill, Julie demands to talk to Karen as proof of Kevin's illness. When Gail told Julie that Karen is busy at GH trying to fight the virus, she also told Julie that Frank has succumbed to the flu. Julie grows agitated, convinced the whole story is a lie.
When Frank develops cardiac problems, Lark insists that a dose of DL-56 is the only thing that can save him. Eve calls the lab, explains Frank's condition, and asks Karen to give Frank a dose of the drug to keep him alive. Karen agrees and takes the DL-56 to the ER. Before Karen administers the drug, Frank regains consciousness briefly and told Eve, Karen, and Lark that Julie is pregnant.
After giving Frank the DL-56, Karen begins to show symptoms of the flu. Eve offers to take her into a treatment room, but Karen refuses to stop working on her vaccine research. Matt visits Ellen, who regains consciousness and, much to Matt's relief, recognizes him. Eve calls Gail at the jail to tell her that Julie might be pregnant. When Gail asks Julie if she is pregnant, Julie's paranoia escalates. She tells Gail she refuses to have a pregnancy test because she believes "they" will try to take her baby away from her.
With Lark at his side, Frank regains consciousness and shows remarkable signs of improvement, including a healthy appetite. When Eve told him that the ER is under quarantine and he can't lave, Frank becomes violent and rips out his IV.
Back in lab, Matt told Karen and Eve that first batch of vaccine is a failure--all the test rats he gave it to have died. In desperation, Karen suggests they take Frank's recovery as a cue and administer DL-56 to all the patients infected with the flu. Eve argues that the side effects are too dangerous, but Karen pleads with them to see that DL-56 might be the only hope they have of stopping the virus before it takes the lives of all the people they love.
In Greece, Joe and Courtney convince the cafe owner to let them stay the night in the room above his place. When he shows them to the room, Joe is more than uncomfortable about the fact that the room has only one small bed. He asks for some blankets and told Courtney he plans to sleep on the floor, but she tries to convince him to sleep in the bed with her. When he refuses, Courtney strips down to her bra and panties and climbs into the bed by herself.
In Greece, Joe shows Courtney a newspaper carrying their pictures and a story about their detention at the airport and escape from deportation. Courtney begins to panic, but Joe calms her. He cooks up a plan to alert Neil to their presence at the doctor's office. He told Courtney that he'll write a note on a baseball and have a local boy toss the ball to Neil. Later, when they put the plan into effect, the ball went astray before Neil can read the note.
Eve told Karen that Frank is still showing aggression, but it doing well after his injection of DL-56. Karen told Eve that a straight dose of DL-56 has killed all the rats infected with the virus. Matt arrives with Frank's blood test results, which show that Frank's system is full of antibodies they may be able to use to create a vaccine.
After learning that Frank is recovering, Scott meets up with Karen and learns that she has been infected with the virus. He tries to get her to rest, but she told him she has to continue her research on the vaccine. When Scott asks her about Frank's recovery, he learns that Frank has been taking DL-56 for months, and that his recovery doesn't mean anyone else can be treated for the flu.
A while later, Scott brought food to the lab where Karen and Eve are working on extracting the antibodies from Frank's blood. Distracted by Scott, Eve accidentally drops the sample, and declares they have to start all over again. When Scott offers to help clean up the mess, Eve and Karen tell him the whole backstory about Frank's addiction and Chris's responsibility for creating the mutated virus. Scott leaves the lab to go looking for Chris.
Scott finds Chris on a gurney in the ER and grabs him by the throat, He pulls Chris from the gurney and drags him down the hall to Lucy's room, shouting angry accusations at him. In Lucy's room, Scott grabs Chris by the throat, but Lucy awakens in time to stop Scott from strangling him. Chris went into convulsions, and Scott calls a nurse who administers a drug, which improves his condition. Chris told Scott he never intended to hurt anyone. Scott told Lucy the truth about the virus and lets her know that Kevin has become quite ill.
Later in the lab, Karen, Eve, and Matt report to Dr. Perry that the infected rats they have exposed to the antibody/DL-56 compound are showing signs of recovery. He congratulates them, but told them they can't begin using the drug on humans until they've done further testing and have received FDA approval. Frustrated and angry over the notion that people might die while they wait for approval, Karen injects herself with the compound.