three people need organ transplants, two of them are about to die. They have a woman who just died of an overdose and cox insists on bypassing procedure, harvesting her and doing the transplants as soon as possible. It all goes well until it turns out the woman didn't die of an overdose, she died of rabbies, which they would have known if they tested, but its so rare that cox thought there was no way it was rabbies.
Two people die from the transplants and cox almost has a breakdown from the guilt, JD tries to lift his mood and almost succeeds, but then on cue Cox's pager beeps and the third person they did the transplant to also dies. Catch being, the third guy could have waited a few more months for a new kidney, it wasn't an emergency, and if cox hadn't rushed it he'd still be alive, the episode ends with cox having a silent breakdown and leaving the hospital mid shift after essentially killing 3 people due to negligence brought on by obsession.
House doesn't have blood on his hands, Cox does.