"Chem. panel was normal, haematocrit and coagulation factors were within normal limits, and the CBC showed a somewhat raised white cell count – 12,000; nothing significant. The ABG – " Foreman referred to his notes, " – did show a higher than normal level of CO2, but that's only to be expected after a respiratory problem."

Cameron took up the exchange.

"There's nothing in Chase's file about known allergies and no family history of asthma. The level of tryptase was raised but again," she paused, "nothing to substantiate respiratory depression."

"What about the blood smear?" House paced awkwardly across his office.

"Clean." Foreman supplied. "So was x-ray. No fluid, no tumours, no shadows."

"And we can rule out Guillain-Barre: when Chase regained consciousness his impulse was to remove the intubation. Gag reflex is present." Cameron sighed, "Blood pressure is 98 over 65, pulse is 115, temp. is hovering around 98 and pupils are equal and reactive."

House stopped pacing and began bouncing his cane on the floor.

"So what do we have?"

"Chase wrote this when he regained consciousness." Cameron passed the slip of paper to House. He glanced at it briefly before tossing it aside.

"Anything useful?"

"All the tests are inconclusive. Unless we can talk to Chase we've not got much to go on."

"Well thank you, Sherlock." House snapped at Foreman. He stood and limped to the whiteboard, pausing for a moment before beginning to write on it.

Respiratory depression

Arrhythmia

Elevated CO2

Elevated tryptase

Elevated WBC

Tachycardia

Dizziness

Headache

Vomiting

"Is that everything?"

Foreman and Cameron scrutinised the board.

"He had a cold" Cameron offered, shrugging at its seeming insignificance.

House hesitated a moment, then inclined his head. He added sneezing and blocked nose to the list.

"So what explains these symptoms?"

They all studied the list, each lost in their own thoughts as they tried to put together a picture that explained the catalogue of symptoms that confronted them.

"Maybe there's an embolism. It would explain the rapidity of the onset and the severity of the symptoms. It doesn't explain everything, but the respiratory depression and the concomitant tachycardia and ventricular fibrillation were acute onset – maybe the other symptoms are something else." Cameron said, sounding quietly confident in her diagnosis.

"Two conditions?" Foreman asked sceptically.

"Why not? It's perfectly feasible. The headache, vomiting, stuffy nose… they're fairly common symptoms. It's not unreasonable that Chase had something as simple as a cold."

"The chest x-ray was clear."

"The embolism could have migrated."

"Aren't we stretching it a bit now?"

"Why?" Cameron asked, somewhat indignantly.

"It's not an embolism." House stated simply.

"Why not?" Cameron asked again.

"When was the last time you saw a pulmonary embolism present with altered mental status?"

"It might have originated in the brain."

House merely answered this with a glare. "What else?"

"It looks like anaphylaxis." Foreman said simply.

"You're right, it does." House nodded, his eyes remaining on the board. "But it can't be."

"Why not? The symptoms all fit, right down to the sneezing and nasal congestion. Chase thought he had a cold, but it could have been the beginning of an allergic reaction."

House shook his head.

"The onset of arrhythmia was delayed. Anaphylaxis is rapid."

"Maybe there was continued exposure to the antigen"

House raised his eyes at the suggestion.

"Unlikely… but give him a 200mg hydrocortisone i.v. and check for urticaria – anaphylaxis rarely presents without some other sign of allergic reaction. Assume it's not anaphylaxis. What else have we got?"

Foreman ran a hand over his face.

"We need to do more tests."

"Tests for what?" Cameron snapped, "We don't know anything."

"Think." House exclaimed. "We have list of symptoms and an idea of onset. What does it all mean?"

House's outburst was followed by a minute of silence.

"Maybe…" Cameron spoke hesitantly, then stopped.

House looked at her for a moment, waiting for her to continue. When she didn't, he spoke.

"Maybe what? Are we meant to guess?"

"I…" Cameron stopped again, considering what she was trying to say.

"I don't know if this is anything, but yesterday…"

"Yesterday…?" House prompted.

"Chase was… he was… strange." Cameron stopped herself, not wanting to say 'drunk'.

"Strange?" Foreman asked.

"Strange?" House repeated. "Is that some new fangled medical term you youngsters are using nowadays? 'Cause if it is you're going to have to explain it to an old coot like me"

"He was… his behaviour. It was almost as if he was…" Cameron hesitated again then, weighing her concerns over keeping a secret against the potential significance of what she had to say, "… as if he was drunk."

A minute of silence followed this statement; House and Foreman contemplating any implications it may have for diagnosis.

"Could you be more specific?" Foreman asked, his brow creased as he deliberated the new information.

"I don't know. He was… it was like he was… high." Cameron finished lamely, embarrassed at her lack of articulation.

"High?"

"Yeah, you know? Giggly, wild… a bit manic."

"Chase wouldn't come in drunk. I know he can be a bit… self-interested, but he just wouldn't do that." Foreman spoke emphatically, the furrows in his brow deepening.

House looked at Foreman contemplatively, somewhat disarmed by the unusual display of support he was displaying toward Chase – the relationship between the two rarely seemed more than forced civility. His silence continued as a grim but logical conclusion came to him.

"Was Chase using anything?"

"What!" Cameron exclaimed.

"It makes sense. From the ventricular fibrillation and the respiratory distress to the nasal irritation. So what was it? Cocaine?" He looked to Cameron and Foreman as if seeking confirmation.

"Chase wouldn't…" Cameron began, but was cut off.

"Oh, spare me the well-meaning objections. If he's on something I need to know what it is." He looked at Foreman and Cameron's dark expressions.

"Well?"

"House…"

He stared at the young pair of doctors, daring them to challenge him again.

"Just run a tox. screen. Find me when the results are in."