I understand that the DM invested time and energy in creating a scenario (I have thought up quite a few, and even worked a bit on creating brand new game systems, even though I dont personally play-- I understand the work he invested.) however, spontaneity, and completely batshit choices of players are part and parcel of a good Pen and Paper experience. If you want a hard-scripted game, you are better off with an "on-rails" computer game.
Yes, he allowed the character to exist, believing he could simply kill the character, and move along. When that didn't happen, he didn't lighten up at all. The "This is serious, bro!" attitude of many DMs, when it is clear that at least some of your players would prefer a more light-hearted (and by that I mean farcical) play experience, which they blatantly ignore because they totally want to stick to the script, is what causes this kind of altercation. Sheer blind luck allowed Henderson to stay going, along with the DM's unwillingness to actually read and properly enforce the character's backstory. (Absurd characters are fine, as long as they stay to their own backstories IMHO. I remember hearing another infamous tale about an AD&D sorc. character that had suffered a magical accident, and now had Multiple Personality Disorder every time he cast a spell, each with a different manifest behavioral disorder of their own-- Controlled by a random spinner wheel the player had cobbled together. This sorc ended up trying to have intercourse with an offering box linked to a plane of hell, and losing his genitals, IIRC, after spinning "inappropriate sexual conduct" or something like that. Reading that story was about as amusing as reading the tale of Old Man Henderson last night. The sorc stayed in the lines of his backstory, and it was fine as far as I am concerned.) Instead, he was cocky, and sure of himself that he could just kill off whatever abomination the player had created with the equivalent of a deus-ex-machina, and get back to HIS story.
That is not how things turned out, through not only outright fabrication on the part of the player, but the player character being radically OP. (Seriously, I am a very skilled person personally, so I know how time constraints on a person's life limits ones actual desired pursuits. Henderson would not have been able to exist, AND have his weed intoxicated leisurely lifestyle), and sheer dumb luck. But Henderson was a farce-- always was intended as such, and was designed to be as disruptive as possible. Kudos to the DM for allowing him, but bad on the DM for refusing to read all 300 pages of backstory, and chart out the character. Personally, I would have told the player who created him that I would allow him in, AFTER reading and digesting the backstory-- and since it was so long, that would be after tonight's game session. That isn't how it turned out, the DM cut corners feeling cocky, and got burned in exactly the way this farce character was intended burn him.
Part of being a good DM is helping the players have what THEY want from the game time, so that it is enjoyable. Having a stick up your ass does not accomplish this, which is exactly why Henderson was created in the first place. The rest of the job is creating a baseline scenario that the players can either pursue or ignore-- and then enforcing game rules and mechanics. The DM of games like these, with cultists doing seriously screwed up shit, needs to be flexible and rational about his scenario, and what its consequences are.
Take for instance, the cliche "Cultists are summoning eldritch Great Old One [insert name] in the basement of [place] that is near to where the protagonists are-- (naturally)." The protagonists DONT do any investigation at all, and the summoning happens. Now they have no choice but to become involved, as the great old one manifests, and goes to town. The cop-out DM will just end the game here, but this is foolish IMHO. Many of lovecraft's stories START with a successful summoning of a great old one for some purpose-- Like Dunwich Horror. (How did his daughter get knocked up by Yog Sothoth, without Whateley first performing a summoning? Etc.) Not to mention that clearly these kinds of summonings have been happening for some time, as the incantations and spells used to do them are tried and true-- The reason why the Old Ones dont just take over is because the stars aren't right yet. (Lovecraft has outright said so in his mythos.) So, rather than cop-out with 'Game over, you guys suck, this is what you get for not playing my game", what I personally would do, is begin spontaneously creating new story that forcibly involves the player characters simply by the cult doing what the cult wants to do. Such as, once again with the dunwich horror short story, having one of the resulting monsters go on a rampage and tear shit up, but not cause TOTAL destruction. You do this by having deep backstory into why the cultists are doing what they are doing. With a stated goal of their group, it is easier to create new content on the fly that is consistent and believable. It is important to know when to let go of the scenario you have worked up, and dive headfirst into content creation on the fly, when your players require it.
The stated goals you put forth:
1) It is a game about investigation and essentially detective work.
2) It is a game about finding alternative solutions to problems that would otherwise be solved by brute force.
Has a hard "On rails" component with 1). There's more than one way to get caught up with the cult, and then subsequently put it down. Being FORCED to do gumeshoe work is a pathology of a bad GM, and is in this way counterintuitive to your point 2)-- Finding alternative solutions where brute force would solve problems. Brute force takes many forms, including being an abusive GM.
What I am geting at, is that the GM needs to be willing and able to
take a third option, if and when his players NEED him to, and continue down the new road this option creates, leaving the written scenario behind as little more but reference material for locations, items, and motives.
The GM in the Old Man Henderson story is forced to do this, but is dragged kicking and screaming the whole way, rather than going willingly. Again, personally, I would have had a blast with this. After the systematic destruction of a few cult centers, I would have sent high ranking members of the cult to other geographic localities outside the immediate area with news of the distrubances, had them make phone calls (modern setting, after all), Leverage mass mind contamination by exploiting image boards (in story) with memes containing imagery that cause SAN damage to recruit new fodder worldwide through mental compulsion (See the sensation of "What color is the dress!?" recently. Now, imagine a "WTF is this!?" sensation, where part of the image contains magic crazy, which then causes lots and lots of NPCs world wide research the image components, and have some significant portion fail their SAN checks, and become compelled to serve the cult through additional image board postings later-- etc. ) and in general, make the localized brute damage of actions like Henderson not be such a high focus. Cauterize, control, continue. The loss of the local branch of the cult is acceptable, as long as the cult's goals continue to be served; step up the timetable of the local cult's activities, etc. You do this by having the cult go underground, WITHOLDING leads, and progressing the cult's goals to the point where direct involvement is no longer avoidable. Remember, the cult will be investigating the protagonists, even if the protagonists are stumped in investigating the cult!
When I create a scenario, I do it "The tolkien way", where I amass a huge amount of related bits of backstory matter, and then assemble a plot with those elements. All the data is "True"-- and used as needed when a question arises. It takes me months to create a good scenario. To me, a "Good" scenario is freeform, free flowing, and dynamic. It responds to the unexpected because it does not have rails, it is built on consequences and motives. I keep a separation between "Story", and "Data." What's inside containers, who knows what kinds of magic, --- that's all data. Why a person does something, and how they interact with other people-- that's story. I compile huge-- HUUUGE amounts of data, make an indexed notebook with sections to quickly access it, then keep another notebook to track story with. There's the scenario you start with, and there's the story you end with. A good GM often has these two things being different-- at least in my opinion. It allows replay of the same base scenario with different characters and motives, without getting stale as quickly.
@havingPhun
Lovecraft begins to feel too formulaic over time. Contrived sources of people going mad, tortured use of adjectives (Seriously, do you know what
"cyclopean" means, as he uses it? It's JUST stonework that does not follow a regular pattern. How that is supposed to instil fear I dont fathom-- etc.) His critics often called him "The father of tortured adjectives" and the like. Many of his short stories are quite compelling, and sadly tragic- but after awhile, the start to all feel the same. (Has read pretty much every single one of his stories)