The hum of the various laboratory instruments murmured softly in the background as Cameron sat stiffly on her stool, waiting for the mass spectrometer to alert her to its completed analysis.

The whirring machines were strangely hypnotic, she found, and a certain sense of peace had descended upon her since she had entered the room: the droning noise familiar and normal in circumstances that were anything but.

Cameron found it difficult to even conceive of Chase as a drug user, a junkie, and yet… A lingering doubt refused to be dispelled from her mind. Just thinking back to the previous day when Chase had come bursting into the office, eyes wide and barely able to stand upright… She had thought him drunk at the time – it made perfect sense.

She refused to believe it. She didn't want to believe it.

But if not drugs, what?

The unmistakable ping of the equipment roused Cameron from her ruminations and she jerked back to awareness, jumping from her seat in her eagerness to discover what the analysis had revealed.

Pulling the sheet of paper from the tray, Cameron read it fervently.

Sighing heavily, she turned and left the lab, keenly aware that House would be eager to see the results.

………………………

"No trace of drugs, illegal or otherwise."

Cameron dropped the file on the table in front of where House sat, the faintest hint of 'I-told-you-so' in her voice.

"How 'bout that?" House replied, not bothering to read the report.

"Is that all you can say?" Cameron asked, piqued by his lack of contrition.

"What would you prefer?"

"House!"

"Oh, don't get your panties in a twist."

Cameron stared at House in open-mouthed indignation.

"Any signs of uriticaria?"

Cameron continued to stare, disbelieving of House's ability to gloss over the glaring offence he caused others. Biting back a rebuke, she shook her head.

"No. There are no obvious signs of an allergic reaction and the hydrocortisone isn't showing any effect."

As Cameron spoke Foreman entered the room, dropping heavily into a chair.

"So then, what've we got?"

"Nothing." Foreman responded, a trace of despondency in his voice.

Heaving himself up House hobbled to the white board, surveying it closely.

"Right." He said, "What we have here is the involvement of three distinct organ groups. Cardiac, pulmonary and neurological. What can cause these symptoms?"

Foreman sighed, "House, we've been through this already…"

"Don't look at them as a whole," House interrupted, "look at the organ systems, and think."

"The acute pulmonary symptoms presented first – at least that we know of. They could have triggered the cardiac involvement." Cameron offered.

"No." Foreman disagreed, "The neurological symptoms presented at least twenty-four hours before the pulmonary distress. A neurological condition could precipitate all of what we're seeing now."

"How about that? A neurologist seeing a neurological problem."

Foreman shot House a look, but otherwise ignored the jibe.

"There could be an underlying pathology in the brain – a tumour, a bleed, an infection."

"The blood results aren't showing any sign of infection." Cameron interjected.

"It could be an occult infection, localized to a small area of the brain. We really should scan the head…" Foreman looked to House, seeking approval that he really did not need. House's attention, however, was elsewhere.

"House?"

He remained silent, frowning in concentration.

"House?"

Ignoring Foreman House walked to the whiteboard and picked up a pen. He tapped it against the board for a moment, then underlined the symptom altered mental status that had been added to the list earlier.

"So…" He turned back to the room. "Can anyone tell me what we have now?"

Foreman and Cameron exchanged a mystified look.

"Does that even help us?" Foreman asked.

"I think my original question implies that it does."

"So are you going to tell us what, or are we playing twenty questions?" Cameron asked, her voice far more fierce than she intended.

"A toxin." House retorted. "Isn't it obvious? The elevated tryptase, the dizziness, vomiting – a change in behaviour?" House peered at Cameron and Foreman, who, apparently, failed to respond as he had hoped.

"Come on!" He turned to Cameron. "You said he looked like he was drunk, you were right. He was under the influence – just not alcohol."

"What then? This is all speculation, House." Foreman snapped.

"Well that is what we need to work out. What are the most likely sources of toxin exposure?"

Foreman sighed, clearly impatient at the new direction they were taking.

"Environmental, dietary, accidental…" Cameron intoned, sounding little convinced. "Routes of exposure could have been through inhalation, ingestion, or absorption. If we are talking about a toxin the symptoms don't really preclude any of the possibilities."

"Absorption is the least likely." Foreman added, "There's no evidence of skin irritation and the eyes are clear… So how could have exposure occurred?"

"Dietary is out." House said, "Chase eats in the cafeteria same as everyone else. If that was the source there'd be other cases. So what toxins could he have come into contact with here at the hospital?"

"Chase is an intensivist" Cameron said, "he works with dozens of different drugs everyday, but he's careful. There's no way he could have exposed himself to dangerous chemicals."

"Outside of the hospital then. His apartment, the grocery store, a lap-dancing club – where might he have been?"

"His apartment seems the most obvious place to look – after here it's the place he spends the most time, but all the same, what toxins are there likely to be in an apartment building?"

"You'd be surprised." Cameron answered. "You look in any kitchen or bathroom and there are dozens of dangerous chemicals. Ammonia, chloric acid, ethanol, sodium dichromate, polytetrafluoroethene –"

"Does Chase strike you as the kind of person who spends a lot of time cleaning toilets?" House interrupted.

Cameron glared at him, "But you get my point?" she said scathingly. "Chase could have been exposed to any number of chemicals."

"Yes, I get your point. So why don't you…" he stopped mid-sentence, an expression of comprehension arching his features.

"What is it?"

House did not answer for a moment.

"Did Chase say that Jameson lived next to a gas station?"

"What?" Cameron asked, confused by the sudden change of subject.

"Stan Jameson! The patient we've been treating for the past few days. Does he live next to a gas station?"

"Uh, I think so." Foreman replied, flicking through his notes for confirmation. "Yeah." He looked up, "Why?"

"Gas stations," House said, "sell gas. Can anyone tell me what a primary component of gasoline is?" He looked to Foreman and Cameron, taking in their bewildered faces.

"What has gas got to do with –" Foreman began, but was cut off by House.

"Benzene. That's what. Benzene has got everything to do with this."

"Benzene?"

House nodded.

"It fits perfectly, both for Jameson and Chase. Jameson presents with aplastic anaemia, Chase with rapid onset of respiratory and cardiac symptoms. Jameson is the classic case of chronic exposure, Chase of acute. It makes sense!"

"Benzene is known for its odour, there's no way Jameson or Chase could have missed it."

"Why not? Jameson lived next to the gas station for years. The sensors of the olfactory receptor cells would have been saturated before he'd finished unpacking."

"And Chase?"

House thought a moment before responding.

"He had a cold. Blocked nose equals dulled senses. He didn't smell the benzene because he couldn't…" Finding his explanations had not yet convinced, he continued.

"Think about it. Chase went to Jameson's house yesterday and returned behaving like he was on the business end of a liquid lunch. Euphoria is a classic symptom of acute benzene poisoning. He came in this morning and could barely string a sentence together. Again, classic presentation of CNS depression. He goes back to Jameson's house and sure enough the progression increases pace. We've got respiratory depression, ventricular fibrillation, tachycardia – it fits."

House finished speaking and a brief silence fell.

"What do you want us to do?" Cameron asked.

"Go to Jameson's house. We need samples; we need to know exactly what we're dealing with."

"You want us to go to Jameson's house? After telling us the place is contaminated with benzene, you want us to go there?" Foreman glared at House, astonished at his request.

"Don't spend more than five minutes in there and you'll be fine. Ten minutes, tops."