Serving

History has not recorded who in the group is responsible for this one alternative profession. 
Was it someone from the serving side, or did a guest commit this particular slip? 
We don't know. 

But this secretive profession does exist: the Observers. 
Now it's no longer about "or" and "not" — it's about what's creeping, combining, evaluating, and consequential, when the observer or observeress gets to work. No commotion, no threatening gestures, no obvious action. The job description lists discretion, inconspicuousness, and the appearance of non-involvement in the large print.

So what do these people actually do all the livelong day? Why, observe — I know that much. But what does that mean in practice? When an observer — or observator? — gets to work, it officially happens rather incidentally. The grey mice of the watching world want one thing above all: not to be discovered, not to be seen, and not to be watched themselves. They are the team of the suspicious, who want to inform first themselves, and then their superiors. This isn't generally about any particular group of people who have given themselves over to criminal behaviour. They observe in order to understand. They observe everything that might contribute. Their work is always varied, even if the realistic execution of it can seem quite tedious.

When a threat looms over a group of people or an institution — a threat assembled from clues and hints gathered by observers — then security may be at risk. And so the building and the group get observed. Watched, that is. While one is at it with the cheerful-silent observing, the behaviour of people and animals gets noted and subsequently evaluated. One is, after all, busy learning for the whole of one's life. When a doctor examines a patient to find the fault in the body's biological-medical system, that doctor has, rather incidentally, become an observer too.

Does serving or observing make you happy? No idea — but in certain situations, what's been observed is surely useful. Because this act of watching and evaluating is one of the fundamental activities through which humanity creates knowledge.
Or something like that.