A/N: Friday update! Woo. I really hope I don't run out of buffer chapters, though. ^_^'' Always something else going on, and I've been dabbling in writing some other fics too.

In the forensics lab, Silver watched as an agent in a lab coat drew a brilliantly red tubule of blood from Shadow's arm.

"We're going to have to compare this against the stock sample of your regular blood," explained the scientist. "Just give me a minute to find the data."

"Do all G.U.N. agents have stock blood samples?" asked Silver curiously.

"Most of them, yeah," said Shadow, disdainfully tossing aside the bandage he'd been offered. "Everyone has unique antibodies and hormone levels and blood type and such, so most agents have a small blood sample electronically documented in case the lab has to test for diseases or poisons later. Or identify their bodies." He rolled his eyes when Silver winced. "Besides, my blood is weird anyway. It's got a lot of Black Arms alien junk in it, so they need to know what it looks like normally if they ever want to find what's wrong with it—like now."

"Found the data!" called the scientist from across the room, hunching over an ancient-looking desktop computer. "Just let me run a few scans on this new sample now, and test for any new substances present."

"Take your time, Alf," said Shadow resignedly. "We need reliable data."

"How long will it take?" asked Silver, fiddling with his fingers anxiously.

"About half an hour, maybe. Feel free to look around, but don't touch stuff," said Alf.

Silver, taking the invitation, began to prowl cautiously around the lab and peer at all the machinery and chemical vials. Shadow had seen all of this before, so he continued to sit on the lab bench where he'd been perched for his blood sample. Still, he watched Silver with one eye, vaguely diverted by the younger hedgehog's fascination with lab equipment.

Silver eventually wandered over to the part of the room where the lab drawers were, each labelled with the name of the agent it belonged to. He paused, running his eyes over the various names idly. Shadow braced for the inevitable question, and sure enough it came:

"Rouge?" Silver looked over, his eyebrows raised. "Rouge is a—"

"Forensics agent, yes," said Shadow wearily. "In her spare time. It's extra pay, and she was good at it. She never used that drawer very much though, she usually worked at home."

There was a pause.

"Don't use past tense," said Silver quietly. Shadow grunted and stood up.

"Whatever. I'm going to clean up while we're waiting, dried blood itches."

"Probably shouldn't run around looking like that anyway," said Silver ruefully.

"This?" Shadow was already halfway out the door. "In G.U.N., this is nothing."

He returned fifteen minutes later, blood-free and with slightly tousled quills; Silver couldn't help but notice that his shoes were as wet as the rest of him. Apparently Shadow really did keep them on at all times, even while showering. Before Silver could comment, Alf came back from the scanner, looking grim.

"There's nothing wrong with your blood," he announced.

"Nothing?" Shadow looked up at him disbelievingly.

"I tested for everything. There's nothing in there that isn't normally in there."

Shadow and Silver looked at each other for a moment.

"Maybe it's the antibodies," said Shadow at last. "I have antibodies that work quickly against poison. They may have destroyed all of it before the test was performed."

"Maybe . . . " said Silver cautiously. "But then, what do we do now?"

Shadow got up, sighing.

"Let me try to milk some poison out of that idiot again, now that he's awake. Wait here a minute."

He disappeared out the door. Alf leaned against a lab bench and watched uneasily as Silver paced back and forth, chewing on the tips of his fingers. Tension hummed thickly in the silent air.

About fifteen minutes later, Shadow came storming back in with a freshly oozing gash across his muzzle.

"There," he said, scraping a handful of blood off his face and slapping it into an empty petri dish. "Test that. Even my antibodies don't work that fast."

Silver cast him a look of mixed horror and admiration.

"Did you—"

"No, it was his idea," said Shadow drily.

Alf ran another series of tests, which went a little faster this time since the necessary equipment was all warmed up already.

"Still nothing," he said quietly.

Silver sank his head into his hands, while Shadow swore roundly.

"What kind of forensics do you call this? There's a poison in there that sends people into instantaneous paralytic shock, and you're telling me you can't find it?!"

Alf shook his head helplessly. Silver looked up.

"The Black Arms alien stuff," he said suddenly.

"What?" growled Shadow.

"You said you had a lot of weird stuff in your blood," said Silver. "What if the poison Sonic's using is one of those things only you have in your blood? What if that's why you're immune to it?"

Shadow processed this for a moment. Then he turned to Alf.

"He has a point. What things are there in my blood that wouldn't be in someone else's?"

"A lot," said Alf, looking over a printout.

"Specifically then," said Shadow impatiently. "Is there anything in my blood that, if it got into someone else's blood, would make them feel really frightened?"

"Let me see . . . " Alf squinted at the finely printed text. "Well, there is an aldehyde-derived molecule that you seem to carry in high levels. Quite rare. In normal people, it binds to receptors in the fear center of the brain, triggering intense but unreasoning terror."

"That's it!" said Shadow, his eyes glinting victoriously.

"But then why aren't you terrified all the time?" asked Silver. "If you have it in your blood non-stop."

"That's a good question," said Alf, scratching his chin. "I would guess that the receptors in your brain are either non-existent, or so constantly saturated by the chemical that your brain no longer responds to the signal."

"You mean . . . he literally can't feel fear?" said Silver, his eyes wide.

"Sounds about right," said Shadow smugly, already heading for the door. "Come on, we have work to do."