Well, the good news is this - of all the places your Investigators will visit in MoN, New York is probably the most familiar of them all, if you're an American at least. Even if you've never been to NYC personally, you've likely seen more than enough media about it. Don't lie - you know the character, the place, the grit, and the dark as well as the light. Its highs and lows. Its ins and outs. The best way to do this if you haven't yet is to watch films, read books, and find material about NYC, especially about its history in the 1920's. Films like King Kong or its remake can help, as can crime dramas and true crime shows. Think Noir, 20's aesthetics when preparing to run New York, and think of other scenarios you may have run in big cities. Describing the weather in January in NYC shouldn't be too hard, but remember it should always be big - there's always a blizzard the night of Elias' murder, the snow always falls hard, the wind always nips. And when it gets dark, when the power goes out from the storm? It's dark, a massive contrast from the bright lights of the city itself. Use the dark to your advantage. Cut the lights when it matters most, and make the Investigators read their sheets by (false) candlelight. I recommend using little LED fake tealights for safety's sake, but flashlights work too.
If you need extra material at the start of the scenario or later on into the chapter, the perennial classic starter scenario Dead Man Stomp does a great job of giving a taste of what some areas of NYC are like, especially near Harlem and the seedier undersides of the city. In fact, the Companion recommends that you use Dead Man Stomp as a sidequest in NYC. If you do, I would recommend sowing in more Nyarlathotep influence, or at least making the Bloody Tongue Cult more prominent in the story. Maybe the Bonato Gang trades with them or does business with them, or more sinister yet, hires crewmen associated with it as brute muscle. The Bonato Gang can even serve as a lead-in to the machinations of Mukunga and the cult in the city, perhaps being an alternative to using Jackson Elias at all. I know what you're thinking there - MoN without Elias? Sounds unthinkable, I know, but remember that Elias is essentially just plot bait - he's there to be the Call to Action for the heroes and little but. He can always be more than just that, and the Companion makes a good point of this, but he doesn't have to be involved at all...
Going back to Dead Man Stomp for a second here, maybe it could even be him that the Bonato Gang is targeting, not Pete Manusco - Pete is just a guy in the wrong place at the wrong time. It'd be just like Mukunga and his ilk to use an ally to do their dirty work, especially to pull one over on the racist whites of the time! And speaking of race - remember that NYC is one of the most eclectic cities in America, and in the 20's that is no exception. This is the era of the Harlem Renaissance, of increased women's rights, of high immigration and change. You're not just going to see white NPCs, so changing the race of characters - or even the gender - is always feasible. In one run of MoN I read, Jackson's gender was changed to female, and she was made into Roger Carlyle's lover. I made Jack Brady a tomboyish woman and a lesbian, just because as stated before I thought the plot twist of "Samus is a Girl" would be funny. If it's doable with Elias, it's doable with any other character. Just make sure that, as with any change to the story, the change is plot-feasible and has a reason to happen.
Similarly, the cultists of the Bloody Tongue can always be made mixed-race. There's absolutely no reason why you wouldn't have white, Hispanic, even female members of the cult attacking your Investigators with prangas, unless of course this does not suit your idea of what the cult is about. Mine were all blacks and whites living in Red Hook and Harlem, and all male because I figured that this branch of the cult would just not be very women-friendly, which gives an obvious reason for tension between Mukunga and M'weru. Perhaps these two don't see eye to eye for that reason? If you really wanted, you could even shift the leadership of who is in charge of which branch of the Bloody Tongue cult - making Mukunga the leader of the Kenyan branch and M'weru the leader of the NYC branch, or just eliminate Mukunga altogether and have M'weru run both branches, only to have her escape last minute. Think of how thrilling it would be to have your players chasing this bigtime cult-leading priestess cross-country, Carmen Sandiego style, before she finally vanishes, only to later corner her at the Mountain of the Black Wind!
But getting back to brass tacks here, and looking at how NYC functions as a chapter... it's short. It's very, very short. You're probably going to realistically, looking at the Complete MoN's simple write-up of it, spend perhaps three or four sessions here. Now compare that to roughly six to eight sessions for the other locations, and that's if you're hitting everything everywhere plus some. Sure, you can flesh it out... but why do so when NYC is not a long part of the campaign, and isn't supposed to be? Don't let it be. Its only purpose is to springboard into the campaign, giving the players an excuse to start the trip, and even then it doesn't have to be the starting point. I know of plenty of runs of MoN that haven't used NYC as its starting point, and then got to it later. If you intend to do this, you are going to need to lengthen NYC substantially, or otherwise shift its clues and cut it out altogether, but be careful with it! If not handled carefully, you will have a massive clue-dump to give your Investigators solely because most of the leads begin here. Treating this chapter with care is therefore of the utmost importance, even if you don't use it as the springboard it's intended to be.
Aside from all that, NYC is not a bad chapter, and has the makings for a short, if well-tied together, standalone scenario. It tries very hard to work with the beginning of a massive campaign, and generally does a good job of it, but it needs some Keeper love to make it more memorable. I would highly recommend throwing in an extra scenario or two to make it more fun and more interesting, or at the very least, a Hunting Horror attack or cult ambush somewhere. As it is, the characters here get swept by the wayside and can be easily forgotten, unless the Keeper is good at fleshing characters out and bringing the character of NYC itself to the forefront. For these reasons, if it were a standalone campaign, I'd give the NYC chapter a score of 6/10 Bloody Tongue Cult sigils. For what it is, it does a good job, but it could probably not stand well on its own. The Keeper must add to it to make it valuable and satisfying to the players of their game.
That all said, let's take a look at how I ended up running this scenario. When it came to Room 410, I ended up surprising my players with an audio recording of a friend on Facebook who read lines I wrote for Elias' frantic phone call. I knew I wanted the intro to MoN to be memorable, and there's nothing more memorable than hearing a character frantically call for help - especially in real life! I found all the sounds of phones ringing and static from the line myself, and modulated it in Audacity to make the call sound authentic. It came off great! I actually wrote two script versions, one of which made it in and the other of which I felt didn't work as well as I wanted. The result came out sounding awesome, and worked really well for the tension of the early parts of the story. As for continuing into Room 410, the players themselves were armed and prepped for an ambush. They nearly expected it of me. What they didn't expect was for it to happen so soon - Kat's character Ralph ended up losing a hand within the first minute of the battle with the cultists, making for an intense start to MoN proper. Of course, prostheses being what they were back then, it only gave him a more intimidating look... and a bonus to Intimidate to boot. From there, the hunt for clues was slightly lackluster by comparison, but it sure gave them a reason to want vengeance!
As I stated earlier, even if you don't remove NYC or alter the starting point of the game, you'll need to lengthen either the front or the back end of the chapter somewhat. It's just so short that there's not much there. I would highly recommend taking a look at Dead Man Stomp, One in Darkness, other short scenarios you can change to fit into NYC (like Dead Light or Edge of Darkness, or even the ever-classic The Haunting), and even some of your own material. The Companion also has a short scenario entitled Last Stand at Fat Maybelle's, ideal for one last battle with the Bloody Tongue Cult should the Ju-Ju House get the better of your Investigators. I opted not to use this material, and instead recycled parts of it for use in the Raid on Ju-Ju House. For example, the entire sequence with the subway and its use to zap the Chakota was ripped straight from Fat Maybelle's, while the eponymous location and owner themselves were never used. I reasoned that there was no need for them, because my version of the NYC Branch of the Bloody Tongue was rather amateurish and had a lot of in-fighting, being a semi-recent splinter group, making them an easy early target for the Investigators.
Instead of that material as a one-off, I reasoned that since my players had gained Erica Carlyle's favor and the Bloody Tongue's attention, they could just stay at her safe house. They really had no trouble convincing her, since one of their number was a Federal Marshall, and eventually she did open up concerning her brother, invited them to a party at her place (which I made a Masquerade ball and even threw in an early Nyarlathotep-in-human's-clothing cameo that nobody picked up on), and they got the info they needed from there. I also knew that at some point, I needed to introduce the Hunting Horrors, because they are kind of Nyarlathotep's pet guard dogs and I wanted the early connection. That ended up, therefore, happening in the safe-house, an out of the blue event that I let progress as it would. There was absolutely no planning involved there, except the idea that I wanted a Hunting Horror to attack them somewhere in New York. The result was completely impromptu, and in my opinion, one of the better parts of NYC.
If you're wondering about Brad going missing during that episode in the blog entries, it was because Aidyn was absent that session and was going to be late the session after. Because I needed a reason for them to investigate Ju-Ju House and wanted to have a sense of urgency, I simply decided to kidnap Brad entirely. Sure, he lost Sanity for his ordeal, but it was a hell of a plan, and it really came off well. By the time they finished investigating and got to Ju-Ju House, tensions were high and so were the stakes. They had no idea what was in there, and no idea what to expect. I ramped up the suspense and energy, included the idea that maybe the Chakota dug the tunnels out with its several teeth, and the rest was just me, them, and the ever deepening sense of urgency.
About the Chakota - it's the crown jewel beast of the Ju-Ju House, and you owe it to yourself and to your players to use it in some fun way. The hints of it should be foreboding and frightening, and the reveal of the beast should be grand. My Investigators worked with the NYPD to raid Ju-Ju House, and easily mopped the floor with the cult, even murdering Mukunga with a well-placed shot to the head. What they didn't expect after freeing Brad was the Chakota. Sure, having the dead Mukunga's corpse fall onto the lever to open the pit was cliche, but it was damn cool to see the Chakota end up chasing them out, only to get fried by the third rail in the subway. It meant that I didn't get to use the zombies or have them find Mukunga's materials - including the awesome Mask of Hayama - but honestly I could take or leave the zombies. I am slightly disappointed in one thing about them, however - I had initially planned, if the group had gone in before a cult ceremony was to occur, for them to find Jackson Elias as one of the reanimated dead, taking massive SAN loss in the process. This unfortunately did not happen, but at least I ended up bringing them to a satisfying means of revenge for both Elias' murder and Brad's kidnapping.
All that was left from there, after letting their Investigators heal up both wounds and sanity, was to decide how to get the Investigators across the pond to any of the other locations. I left the choice up to them, and went with their decision. They decided on London because it had the most clues pointing there, and because they reasoned that taking the fight to the Bloody Tongue in Kenya was just too much, too soon. They had no reason to really go any of the other places to begin with, especially when London was much closer to feeling like home, anyway. Additionally, I needed to delay the start of London because Rob had a prior obligation meaning that I would need a travel interlude so he didn't miss the start of London. Now, I could have used The Mauritania from either The Cthulhu Casebook or Fearful Passages (I forget exactly which one has it), but at the time I didn't have the PDF for it and had no means of obtaining it. So, out of pure necessity and needing to practice my scenario-writing chops, I wrote my own. In fact, most if not all of the travel interludes and side scenarios, including the material on the White Mistress, were made up whole-cloth, but some were from other sources. I'll be talking about those as I get to them, but for now, I'll focus on the cruise.
I settled on a cruise because I felt that was the most feasible option - air travel was just not very common in the 20's, even in 1928, with few exceptions. Besides, tons of crazy things can happen on a cruise, and I really wanted to use Walter Kimble again, the lovable rogue. In fact, the initial plan was to make him sort of a Carmen Sandiego type character, where he'd show up to harangue the Investigators, but I ended up shifting the idea to his being a sort of parallel downfall as he too became wrapped in Nyarlathotep's twisted web. To do that, I needed to have him steal something so the Investigators would run into him again, and I discovered something that might work as the MacGuffin one evening while browsing Reddit's r/Lovecraft and r/Cthulhu subforums. There, I noticed someone had posted a sculpture they had made of Nyarlathotep - a very nicely done sculpture by one u/PhosphorousThoth. That settled the image I had of the item Kimble would steal - an idol of Nyarlathotep - and that very image is present in one of the two blog entries for that part of the scenario. I asked them if I could use the image as a prop and a photo in one of my blog entries for MoN, and they agreed. Phosphorous, if you're reading this, thank you again for letting me use the image of your artwork. And for everyone else, if you're on Reddit and like Lovecraftian stuff, make sure you give him a look and some kudos if you liked the sculpture!
The rest of the scenario then kind of came together organically from there, and within about a week, I had pieced together the bits and pieces needed for the adventure in an old notebook. I've entitled the scenario very simply, The White Maiden, and it can fit as a travel interlude just about anywhere if the Keeper so desires - just replace Walter Kimble with a rogue of your own devising or your campaign's rival du jour. I've placed the notes for it on my Dropbox if you would like to run it for your group, and you can access that material right here. Once I got it started, the scenario went just as planned, and my players loved it. I also added an extra bit from the Companion on having a seance to speak with the dead Jackson Elias, which actually was quite fun and I echoed later on in Cairo with yet another seance, involving a character they previously met on the ship. As for the deceased Elias, he of course was insane and had no idea he was dead; I just couldn't resist having Nyarlathotep butt in on the conversation to freak out my players. It worked a treat, and everyone truly enjoyed it. Honestly, I think it was one of the better mini-sidequests I've ever done!
By the time the group got to London, we were all ready to begin the story proper and get into the meat of it. What we didn't expect was for London to be as exciting as Campeche and New York City. Well, I expected it, of course - but they certainly didn't!