Here's something I've been wondering about. How do Inquisitors come to work on the cases to which they deal with? How does an inquisitor end up on the trail of a cell of heretics? A heretek? A daemon?

Do cases get assigned by some sort of inquisitorial bureaucracy or do Inquisitors have relative leeway with their chosen avenues of investigation?

Most inquisitors are given cases to study and follow up on. If they are currently without a case then they are free to persue any avenue of study and inquiry that they wish. Also some inquisitors can go on their own missions if their ordos leader or direct superior allows them special conditions.

In the case of Eisenhorn he took his mission to his superior who let him continue the investigation. As opposed to Ravenor who chose to go rogue instead of following his superior's instructions to cease following the case he began obsessing over.

I'd go with close to the exact opposite of the above. To my understanding, there isn't much in the way of bureaucracy in the Inquisition. There is a LOT of favour passing, favours owed, life-debts to teachers and masters, etc., but no real bureaucracy. Such would only hamper the Inquisitions primary function and offer an avenue for corruption and exploitation. Likewise, i don't belive Inquisitors can really have direct superors as all are equals (some just get a lot more props then others and occasionally a fancy title to show they're more popular then the other fellas ;-) )With that said, there are many ways for an Inquisitor to get himself onto some trouble:

To become an Inquisitor, one would not only have become quite attuned to what isn't right and the sure signs that things somewhere might be getting worse, but also have the incredible drive to confront that which is wrong, the initiative to do such without someone having told them to do such, and enough crazy to actually seek out and run t words those things most sane folks should rightly run screaming from. To this end, they might stumble upon something that smells a bit fishy, or, more likely, have lesser agents, eyes and ears so-to-speak, keeping tabs on important places and people waiting to report odd or suspicious happenings to the Inquisitor. Old Inquisitors might have such networks of informants in sensitive places that span an entire sector with eyes and ears in most of the centres of power as well as more obscure but sensitive areas where information pertaining to their particular speciality or obsession lie. Younger Inquisitors, however, might only have just a few key locations on one planet under their surveillance while they work on expanding their web of informants.

Where Inquisitors come together and share resources, such as in the Ordos or in the Conclave holdings such as the Tricorn Palace, there would also be ongoing records and reports kept of what is going on out in the sector, sort of like a Byzantine bulletin-board where various Inquisitors can report what they don't mind other Inquisitors knowing, what they're looking into and what they've found just in case they're never heard from again so another Inquisitor can pick up the investigation or avenge their death. It is also in these places where Inquisitors can gather, swap resources and share information with those of a like mind or at least someone they hope to gain something from.

This brings us to the age old favour system. Not only dose an Inquisitor stand a good chance of inheriting a legacy from his days under his master (maybe even an investigation 500 years old and being handed down from one Inquisitor to the next), but just because they received the seal doesn't mean they no longer respect nor remember their master. When an Inquisitor is raised to the seal, their master, the one who helped mould them and form their ideology, doesn't just fade away (unless that's what happened to them, you never know in their line of work). That Inquisitor now has another Inquisitor who, hopefully, respects them and their opinion and who would, more often then not, side with them on important matters, something not to be scoffed at and a wonderful political tool. More then that, they are someone that, chances are, the master can trust -a rare thing indeed in the Inquisition. So, when the master runs into trouble as Inquisitors are want to do, who do you think he will turn to? Either his master, or his former pupil. If he runs across something he can't handle, whether he's too busy or he needs extra guns, then he already should have an ally and one more then willing to assist in the Inquisitor he helped get to that position in the first place and would more then likely call upon him.

Of course, Inquisitors understand that other Inquisitors are all driven men and women and there's a lot of things you just can't do alone. They will hunt out other Inquisitors or haunt the gathering places waiting to be able to offer their services to another who might have something they need, or the clout to help them see their own matters and obsessions through to the end. Do a favour for one, tip them off to something that interested them, and they'll at least owe you the same courtesy if they're worth the courtesy to begin with. Other-times, Inquisitors will find something that demands a specialist, someone who has knowledge or skills they do not, but know of one who dose by reputation or a group of such and seek them out to help tackle this dire threat they've unearthed.

There are many more ways an Inquisitor can find himself on a case... it really all depends on who they are, their style, and who they chose to pursue the Emperors dark works.

In my game, so far, every investigation has pretty much grown organically from the last, continuing ripples for 20 some-odd in-game years from the actions of one mad radical inquisitor. The group is currently engaged in three separate investigations: there's the long view agenda, eradicate the Sloutgh and any Imperial Powers corrupted by them. They are engaged in such based solely on the Inquisitor's own burning hatred for the Worms that Walk. Before he had received his seal, they had made his life a pure hell. In fact, his first mission as a fresh faced and terrified acolyte was against their machinations and it just never really stopped as one terrible thread lead to another in a tapestry of horror and corruption that seems to stretch into the Inquisition it self, something he can not let stand now that he has the power (or dose he?) to do something about it. Then there's a "matter most urgent" which had come up while burred in old archived records in the Tricorn hunting up lore on the worms and any former inelegance that might have been gathered as well as looking through what his deceased mistress had managed to uncover in her files.

While going through his dead mistress' files, an astropathic communication came into the offices she maintained as a central nervous-centre for field reports from her acolytes. The message was encoded in the cyphers he knew from working with her and her former master each as an acolyte. Once deciphered, he came to find it to be a message from one of her acolyte teams that she had sent searching for the members of his former cell. This was an investigation she was engaged in due to her driving goal of bringing down her former master and revealing him as the raving heretic she thought him to be... she was somewhat proud of the fact that she had effectively risen her self to the seal, doing such by seeking out three of her master's most outspoken and hated of enemies and supplicating herself before them, eventually (and with much trial and pain) getting them to raise her to the seal so she could go after her former master unimpeded This eventually brought her into conflict with the PCs cell, one of her former masters last remaining cells in the last years of his life. This, resulted in all the cell members running except for the adept, who wanted to do the "right" thing and turned himself over to her for punishment and purging for his former master's sins along with that same master's head. He wasn't purged and, in fact, he eventually gained her trust, was the last of her acolytes to see her alive, and was the one to execute her last dying orders while bounty-trackers, bloodsworn, and the best trackers she could find hunted down his former cell-mates -he knows he will have to finish that messy business as well.

What the trackers found was something truly horrifying in it's magnitude, a dark conspiracy that gnaws at the very roots of the sector, one that causes them to doubt even the secrecy of the cyphers and the vows of the astropaths necessitating a face to face meeting with her for no one or nothing else could be trusted. And so our Inquisitor set out to meet with his mistress' former acolytes and hopefully pull from them what they've learned. On Fenksworld where the meeting was to happen, the acolytes, of course, turn up dead (when do they not in these situations) and while piecing that murder mystery and puzzle together, the Inquisitor and retune stumble upon another matter by accident, their third investigation.

While seeking a lead to the murder and puzzle of the dead acolyte at the Administratum info-temple in Nova Castilla, the Inquisitor and party were witness to an incredibly strange and tense scene of an irate naval Admiral vs Bureaucracy. The Inquisitor decided, after a casual look into the matters that made the admiral irate, to see about a quick fix and gain the favour of a navy admiral (he's starting to think a lot of planet hopping might be in their future and being in good with the Navy could most definitely help with such). In doing so, he suddenly found himself embroiled in the middle of an escalating conflict over the tithe-grade of Fenksworld chock full of inter-departmento rivalry within the Administratum, greedy merchant barons, stubborn naval officers, crime-barons looking for the big score, and, if they look deeper, a far darker threat looking to exploit the whole sticky mess.

So, currently they are engaged in one investigation as a personal holdover from their Inquisitor's days as an acolyte, another due to the legacy of said Inquisitor's last master/mistress, and another that they stumbled onto due to a touch of luck and a bit of an opportunistic leaning. I haven't even had a chance to touch on the reasons the Inquisitor was raised to the seal in the first place and what that will entail for him and compel him to do, the favours he owes to some of the elder Inquisitors who helped shield him from some of the more hot-headed inquisitors who were outraged at his ascension, exploring what he could do for his ordo, etc.

tl:dr... how dose an Inquisitor get cases to investigate? Just by being driven enough and crazy enough to be an Inquisitor in the first place.