House enters the apartment. He soon notices a bird on the balcony that keeps flying into a brick wall. He calls Cameron and tells her he found a blind bird. Only problem is, he hasn't caught it yet. He hangs up on Cameron to go catch it. The biopsy team keeps getting ready.
House stalks the blind pigeon, his cane ready to strike. He corners the bird, but it flies away before he gets close enough to hit it. House watches his last chance to prevent Foreman from brain damage fly into the New Jersey sky. But he doesn't get much time to mourn this, as he notices a dripping pipe directly overheard.
Cameron gets a call from House. "Better have the bird," she answers. Proxy Cameron is pretty hardcore, you guys. She doesn't even say "hello" anymore! I like it. House says he "screwed up." "How can you not capture a blind bird?" Cameron asks. House says that he meant he screwed up last time he went to Joe's apartment; he didn't take into consideration the time that he went there was different than the time Foreman was there. Joe's weed irrigation system is on a timer. (Seriously, that guy had the most advanced set-up for home weed use I've ever seen. Of course, that's based on the only other person I've ever seen try to grow his own weed at home, who just had one little plant in a terrarium with a heat lamp over it. He used a watering can and non-pigeon fertilizer and is alive to this day.) Cameron says that she tested all the water in Joe's apartment and found nothing. House just hangs up on her. Foreman's O2 drops to eighty-nine, and the surgical team look at her for the signal.
Meanwhile, House is examining the weed shed's pipes to find their water source. The pipes lead to the roof. Even with his bum leg, House manages to climb a ladder to the roof, where he finds an open reservoir of water surrounding by thirsty pigeons.
Cameron gets a call from House, who is bent over the microscope he brought to the apartment with him for rapid testing. He says he found a water supply that they didn't test, and it's "riddled with Naegleria," an amoebic parasite. "I know," Cameron says, looking and sounding like she's just been punched in the gut. She's looking at a Naegleria bacterium right now in the results of Foreman's biopsy. House's brainstorm came too late. "I thought I had no choice," Cameron says. And, you know, she really didn't, what with House hanging up on her, and Foreman being about to die from heart failure.
Cameron finds Daddy Foreman in the chapel and tells him that they figured out what's wrong with his son: primary amebic meningoencephalitis. I guess Foreman was exposed to it when he went to the weed shed right after it had been watered, and breathed in some water droplets filled with the stuff. Daddy Foreman asks whether it's treatable. Cameron says that they've started Foreman on anti-parasite stuff that should heal him right up, even though primary amebic meningoencephalitis is extremely fatal -- even AFTER the diagnosis has been made. It has a 97% mortality rate, and those are the cases that have been diagnosed. And those who are lucky enough to survive it, of which there are only SIX PEOPLE IN THE WORLD, are almost always left with severe brain damage. Fortunately, things like spinal taps can make diagnosing this condition a relatively fast and easy process. Too bad no one on this show actually thought to do this even though they usually do spinal taps at the drop of a hat. I know we have to suspend our disbelief and accept medical inaccuracies for the sake of good drama, and most of the time I'm fine with that, but this was pretty ridiculous. If you don't want the disease of the week to be something that causes irreversible brain damage and is 97% fatal even with a diagnosis, then don't choose a disease that causes irreversible brain damage and is 97% fatal even with a diagnosis.