Greta is an Air Force captain who is training to be an astronaut. While in the simulator, she experiences a sudden episode of synasthesia a neurological condition where the senses get their wires crossed, and one can hear vision or taste sounds and crashes. She wants to find and fix what is wrong with her, but doesnt want NASA to know, so she offers House $50,000 to admit her and solve her case off the books.
House, meanwhile, has 40 applicants for his three underling positions. He presents Gretas case to them but tells them that no records can be kept of her stay. Under questioning from the group, Greta reports that the symptoms are new and shes never had similar episodes before. She has no psychiatric history and is on no medications of any kind. She does admit to doing a lot of flying as one student suspects that the prolonged immobility from flying has led her to develop deep vein thromboses (clots) of the legs, which are breaking apart and traveling through her circulatory system and a PFO (patent foramen ovale, an abnormal hole in the heart) and causing strokes, which caused her synasthesia. House orders an EEG, MRI, angiogram, and lumbar puncture, as well as a whole battery of lab tests. He also sends a trio of applicants to search her house.
The radiology studies are all normal, and the only significant blood abnormality is an elevated red blood cell count. The inspection of Gretas apartment revealed a broken fireplace flu flue. The suspicion now is that she has developed carbon monoxide poisoning and she is placed in a hyperbaric chamber (a high pressure chamber that will drive the carbon monoxide out of her cells and replace it with oxygen). As she is getting set-up for the chamber, Greta develops tachycardia (an abnormally fast heart rate), tachypnea (an abnormally fast respiratory rate), low blood pressure, and passes out. The applicants start a code, providing CPR and code medications (but did they check a pulse before beginning CPR?). When the monitors show her to be in ventricular fibrillation, one of the applicants defibrillates her. It restores her to a normal heart rhythm, but also starts a fire in the oxygen-rich environment of the hyperbaric chamber. The fire is put out, and Greta is started on nitroglycerin and blood thinners (heparin, probably) for a suspected heart attack.
With symptoms now consisting of synasthesia, increased red blood cell count, and a heart attack, House throws the case to the applicants again. They suggest Takayasus Arteritis(inflammation of the aorta and other large arteries) and Whipples Disease (a rare bowel disease which doesnt seem to fit at all). An older applicant makes a good case for cardiomyopathy (a heart condition that leads to weakening of the heart muscle), and a transeosphageal echocardiogram is ordered (an echocardiogram that looks at the heart through the esophagus it provides better images of certain parts of the heart, particularly the valves. Frankly, a regular echocardiogram should have been sufficient, but then we would have missed the reveal and character moment at the end). The echo reveals a structurally normal heart, but brief episodes of an irregular rhythm: atrial flutter. A thyroid problem is now the suspect, and a TRH stimulation test (an old and rarely used thyroid test) is ordered. As the test is administered, Gretas heart rate and BP rise and she complains of feeling warm. She suffers another synasthesia episode as well as a psychotic break (or panic attack, depending on whom you listen to). She runs into a conference room and locks the door. She is persuaded to come out (threatened, really), and sedated but not before Cuddy realizes something is going on.
The thyroid results were normal, so one of the applicants suggests a liver problem more specifically: liver cancer with an associated paraneoplastic syndrome. The difficulty is that the Cuddy wont let them run any more tests without the patients name on them, and the patient wont allow her name to be used. House has to figure out how to diagnose Greta without running standard tests. An applicant suggests loading Greta with intravenous Vitamin D and placing her on a tanning bed (because Vitamin D requires sunlight to function effectively and is metabolized in the liver but it would take a huge dose of Vitamin D to accomplish this ) while another suggests giving her tequila to see how much alcohol her liver can tolerate. Unsurprisingly, House goes with the tequila option. While Houses team is administering the test, Greta develops severe shortness of breath. She wont let the team intubate her or give her oxygen because it will show up in the records. Listening to her lungs, House detects a mass and suspects she has lung cancer. Greta refuses a biopsy because it will leave a scar. One of the applicants, a plastic surgeon, suggests giving Greta a cosmetic procedure to explain away the scars, and performing a lung biopsy during the procedure. Reluctantly, Great agrees to a breast augmentation. The surgical lung examination reveals multiple cysts within her lungs. The diagnosis now includes Alveolar Hydadtid Disease (a parasitic disease caused by tiny tapeworms) and pulmonary Langerhans (a disease caused by a proliferation of a line of abnormal cells, in this case in the lungs), but none of them quite fit the case. Chase appears in the gallery and suggests Von Hipple-Lindau disease (a rare genetic disease that causes tumors and cysts to grow throughout the body) with a pheochromacytoma (a tumor that releases high levels of adrenalin and similar compounds, it can be associated with certain types of Von Hippel-Lindau). The Von Hippel-Lindau explains the masses and increased red blood cells, while the pheochromocytoma explains the cardiac and neurological symptoms. The cysts and tumors are removed, but Greta is cautioned that Von Hippel-Lindau is a genetic disease and they could recur at any time. House tells Greta that he has reported her situation to NASA, but it turns out that he is lying and he only told her that to stop the applicants from reporting it to NASA themselves. In the end he picks his applicants, confronts Cameron in the ER (where she now works), and accuses one of the applicants (correctly) of not being a doctor, but hires him anyway as an assistant.