"Anyvun not vearing team colors is fair game," says the Medic. "Anyvun vearing team colors und acting strangely, such as an Engineer not fixing his equipment or anozzer Medic failing to use his medigun, may be a spy in disguise und is fair game for vun strike. If you find ze intelligence room of ze enemy und his briefcase full of papers, fetch it back to our own room as fast as you can und let nossink stop you."

It's remarkably simple, when it comes right down to it.