Clarence, an inmate on death row starts seeing hallucinations of the people he killed -- his girlfriend, a rival gang member and a cop. Clarence screams to be let out of the room and then collapses on the floor.
House barges into Cuddy's office when he notices that Stacy is there. He demands to be given Clarence's case because he is intrigued that the patient's heart was beating so quickly to cause the body to pump air instead of blood. Cuddy reluctantly gives him the case and House sets off for the prison.
Dr. Cameron sees a patient named Cindy who needs a health clearance for her new job. Cindy appears to be a little anemic, and the employer sent her to the hospital for more tests. Cameron is surprised by what is on the x-ray and turns to Dr. Wilson for confirmation. Although it seems obvious what the patient is afflicted with, she only suffers from a slight cough. This doesn't make sense.
House diagnoses Clarence as hypoxic with fluid in his lungs. He will die in an hour without a respirator. The prison warden isn't very sympathetic, but House calls for an ambulance. The warden insists that no death row inmate leave through the front doors. House has Stacy acquire a legal injunction and Cuddy is enraged by him pulling strings for this.
Cameron presents Cindy's file to House, who immediately dismisses it as metastatic squamous cell lung cancer. The patient may have only six months to live. Cameron begs him to think of other ideas, but he urges her to inform Cindy that she is dying. Cameron can't believe that House will treat a death row inmate over Cindy. Foreman thinks heroin might be the cause of Clarence's tachycardia and pulmonary edema, so House orders a drug test.
House's team examines Clarence, but he awakes and freaks out. The guards struggle to restrain him. The results come back with no sign of opiates in Clarence's system. As the doctors try to figure out causes and symptoms for the heart troubles, Stacy glares at House from the hallway. House shuts the blinds to his office and requests an arterial blood gas test. After the meeting, Stacy corners House and demands to know if she can trust him. Obviously, she can't.
Foreman draws blood from Clarence's femoral artery. The tests results indicate a new symptom -- anion gap acidosis. Is it possible that Clarence thought he was taking heroin in prison but was really injecting something else? The team mulls over the causes of anion gap acidosis, and Cameron throws out INH, the drug for tuberculosis. House sends Chase to the prison to find Clarence's secret stash.
Wilson finds House watching television in a coma patient's room. Wilson wonders whether House only needs people to like him because he needs people to help him get things done. If Stacy can't trust him, he can't use her. Suddenly, House gets a page that Clarence is dying. He injects him with atropine to buy a few hours. House calls Chase to see if he found anything, but Chase has only found boxes with office supplies in Clarence's cell.
House visits Clarence and pours him a shot of 150-proof rum, explaining that a dying man deserves one last drink. He asks Clarence why he tried to kill himself by ingesting copier fluid. Clarence admits that he wanted to take control of his life. House tells Clarence that the copier fluid contains methanol, which is poisonous. But the rum they just drank contains so much ethanol that it's going to bind with the formic acid. Clarence will merely pee out the toxins.
Stacy asks if Clarence is clear to return to death row, but House still thinks the man is sick. Cameron stakes out a small area on the white board in House's office for Cindy's symptoms. House comes in and immediately erases it to change the topic back to Clarence. Why would he try to kill himself after filing for an appeal? The other lingering question is why his heart went nuts before drinking the copier fluid. House orders a full battery of tests. Yet Chase and Foreman see that Clarence's CT scan is completely normal.
House later returns to his office to find Cameron sitting in his chair. She wants a procedure that could possibly indicate Cindy doesn't have cancer. House says a biopsy would be more definitive but denies the request. Cameron lights into him. He finally agrees that if she covers two of his clinic hours, Cameron can run her test on Cindy. Cameron inserts a bronchoscope into Cindy's nose and she reports to Wilson that it showed no sign of infection. He tells her that she'll have to biopsy.
Cuddy barges into House's office. Stacy told her about Clarence and he will be sent back to prison. Clarence, meanwhile, complains of tremendous stomach pain, but Cuddy doesn't believe him. House pulls back Clarence's sheets, revealing a large pool of blood on the bed.
The surgeons remove almost a foot of necrotic bowel from Clarence. House starts to wonder why Clarence killed the people he did. They figure that Clarence killed his cheating girlfriend over jealousy, his first cell mate for revenge, and an abusive guard for retribution. But why did he kill the second inmate? House asks Clarence about the anomaly and he doesn't want to talk. House badgers him and Clarence finally opens up. He admits that he felt like the guy could stare straight through him. Clarence just freaked out and killed him.
House, Foreman and Chase ponder the sudden cause of this rage. Chase suggests adrenaline, but House tells them about pheochromocytoma which sits on top of the adrenal gland and spits out adrenaline randomly. Although extremely rare, it explains everything.
Wilson discusses Cindy's diagnosis with Cameron. The biopsy was positive and she is terminal. Cameron says that she just spending time with Cindy because she has nobody else. The woman's parents are dead and she has no siblings. Wilson tells her it's not worth it and could mess her up for years. Cameron thinks that when a good person dies, somebody should notice and get upset.
House tells Clarence that he will need an MRI to confirm the diagnosis. However, Clarence has prison tattoos which are usually made with heavy metal causing the MRI to suck them. Clarence refuses to have the tattoos removed, and the MRI still shows the pheochromocytoma. After the treatment, Clarence is cured.
Foreman talks with House about Clarence's tumor. Since it explained the rage attacks, it possibly explains Clarence's murders. Foreman plans to testify at Clarence's appeal hearing. House says that a small tumor doesn't absolve Clarence of what he did. Plenty of other people managed pheo rage attacks on their own.
Cameron hugs Cindy as she gives her the final diagnosis.