Mr. Plutus, or Mystery Infection Guy is House's unseen patient in the episode 5 to 9.
The patient needed a liver transplant, so Dr. House bribed the physical plant staff to turn on the air-conditioning in Dr. Hourani's operating room in an attempt to hurry him up so he could get it. By this point, the patient was covered in boils and had an abcess as large as a fist. Dr. Cuddy arranged to have the heat turned back on and promissed Dr. House he could have the OR next.
However, before they could anethetize him, the patient started having hallucinations. His blood pressure was falling and his heart rate was rising, indicating congestive heart failure. Dr. Cuddy still would not allow Dr. House to infect the patient with malaria. However, Dr. House didn't think it was congestive heart failure.
Dr. House did further tests and found renal cell carcinoma. Dr. House wanted to treat him with malaria and chemotherapy and went back to Dr. Cuddy for approval. He told her that he was trying to make the patient hypothermia and malaria was the cheapest way to do it. Dr. Cuddy realized Dr. House was betting with someone that she would approve malaria and refused. Dr. House left the consent form with her for review.
The patient had both liver and kidney failure and Dr. House asked Dr. Cuddy to get Dr. Hourani to do the surgery.
They found a liver for the patient, but Dr. House decided he wanted Dr. Chase to do the surgery instead. Dr. Foreman explained to Dr. Cuddy that Dr. House wanted to prove to the chief of surgery that Dr. Chase was his best surgeon. Dr. Chase also wanted to perform the surgery. However, they needed someone to book the OR who couldn't be overruled by either Dr. House or the chief of surgery, and Dr. Cuddy was the only person with that authority.