This escape room was terrible! Did I do something wrong?

Question

^{Someone told me that I should put a link to Fortnightly Topic Challenge #50: Escape Rooms... whatever that is, sure.}

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PSE, I need your help. I just got back from the worst escape room experience I've ever had in my life. Not only was the solution incredibly obvious, but it was also wrong for some reason. Why is that? Did I miss something? I'm going to put all the puzzles below here, and maybe someone can validate my concerns or tell me where I went wrong.

So, the escape room had a prisoner cell theme, and the goal was to find the five letter password to unlock the lock to my cell and, of course, escape. The first thing I saw when the time started was a letter on the floor. I secretly took a picture of it (I wasn't supposed to have my phone on me, but it didn't seem like the staff cared all that much), and I've transcribed it below:

Dear (insert name here),

So I see that you’re stuck in my cell. That means my plan has worked! Mwahahahaha! Believe it or not, you’re actually the second person to find yourself in this situation after Mr. Cameron, the former PM. I’m not so sure how he got himself stuck in this situation, but it makes for a pretty good fake story, huh?

Don’t be fooled by my amazing storytelling skills though. If you want to escape, you must do one of these things: find the password to the lock, create a tear in the fabric of space-time, or crochet me a cool duck made of down. If you manage to do one of these things - which you won't - then I will concede defeat. And add to my collection of duck plushies. I like my plushies.

Of course, it won’t be that easy to escape my room. After all, I am the proud creator of a logical principle! It’s true - go look it up on my website. And I'm not the only one out here stopping you. My secretary Pepper will do her best to make your life as difficult as possible with annoying questions and creepy fake smiles. My friend Will will terrorize you with insanely hard word clues that will scramble your mind and leave you begging for mercy. And my third cousin twice removed Rick uses a die... maybe. He doesn’t really do anything useful. I'm not really sure why I've kept him around for so long.

There’s really no hope for you, I'm afraid. For example, I won't tell you that the code to escape is five letters long. I also won't tell you that this letter is hiding the first letter of this code, and that the random bold letters tell you what it is. Finally, I won’t, under any circumstances, give you any sort of indication that there's more going on to this puz-I mean, evil scheme than it seems, and that everything I was just talking about is actually a distraction to get you away from the real solution. I won't say anything! Unless, of course, you happen to know the actual location of Mounts Vaea and Silisili. Which you don't, so you are doomed to suffer for eternity!

Ehehehehe... OK, I have to go now. I’m making more of these rooms, and I gotta find out the Dutch national flower. Good luck, and remember that the obvious answer is definitely the right one and not in any way suspicious or contradictory.

Signed,
Red H. Erring

P.S. Ignore the stuff below, I was getting bored while writing this letter and couldn’t get a new sheet of paper.

At the bottom of the letter below the P.S. was this:

RNEZR GFTGA BUULJ DXCCI VQPHQ SWKMY
|o\ = G   /o/ = L   /o- = M   /o\ = N   \o| = T

I didn't understand what the second line of that meant, but I did figure out that the set of letters on the first line did not contain the letter O. Also, the bolded letters in the letter spelt out FOURTH, so I took that to mean the letter D.

There were three pictures on the walls of the room, which obviously I took pictures of. The first one was a grid with some black circles and a single letter U on it. There was a caption below it that said "Must you find the missing parts?".

The second picture was a map of the United States with some of the states labeled, as well as some dots which I assumed were locations of well-known cities. But that didn't seem to matter, since I noticed that the dots form the letter B when connected.

The last picture was a row of figures holding flags. I vaguely remembered a code that used flags - I think it's called semiphore or something like that? - but then I saw that the second line of that extra part in the letter gives me a guide for how to decode the message. It ended up being some kind of gibberish word, but I did see that there was one letter that I didn't use, which was the letter T.

So at the end of all of that, I had five letters which spelled the word DOUBT, and by that point I had already used up almost all the time (the time limit was 30 minutes). Confident that I found the intended answer, I inputted that word into the lock... and it wouldn't open! I tried tugging on it a few more time - still no dice. Unfortunately, I didn't have enough time to ask for additional hints, so I couldn't go back and redo the puzzles. I just kept staring at the pictures on the wall and trying to get the lock to budge until the time was up.

I'm honestly speechless. How can an escape room have such an obvious answer that's not the actual solution? Please help me out here, or else I'm going to lose sleep over this.

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Update 1:

I told my friend about my difficulties with this escape room, and he decided to check it out for himself. Since I didn't manage to reveal any of the hints, he was going to reveal them and report them to me. All of the hints were broadcast through a hidden speaker, and the first one was: "The parts make up a whole. Find how they affect each other." Neither my friend nor I know what that means, but I might as well share that information with you all in case someone can get some sort of idea on how to proceed from that.

Update 2:

Thanks Stiv for helping out with the first couple of puzzles! There's definitely something fishy going on here, and it's not just the letter writer's name. I told my friend over the phone (again, really lax phone policy) to do exactly what was in that answer, then ask for another hint. The hidden speaker turned on again and said this: "The only ciphers you need are the ones you don't discover." So I'm guessing the next step doesn't involve ciphers or coded messages of any sort.

Update 2.5:

My friend and I weren't getting anywhere with that cipher idea, so he asked for another hint. The speaker said: "You are found in only one place, do you see where you belong?" What??? I swear, these people who made this escape room are probably trolling us at this point...

Update 3:

I think Amoz is on the right track with their suggestion of putting the words on to the grid, especially since when you do that, the black dots appear to spell out another word. My friend asked for one more hint, and the speaker replied: "What's missing? It's quite a black and white issue." I guess this is referring to the "missing parts" caption underneath that grid somehow - still not that helpful unfortunately.

Update 3.5

OK, this current hint is really stumping my friend and I, so I had my friend ask for a follow-up. The speaker replied: "Beware the evil influence of the pearls, for even in absence, terror approaches." Um, I thought this wasn't supposed to be a horror-themed escape room? And what's the deal with "pearls" all of a sudden?

Answer 1

^{Okay, there's a lot at play in this puzzle, so I feel a partial answer is justified to get things going and see if anyone can build off the things I have found...}

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First, let's address the 'PS' to the letter, which features this sequence of letters: RNEZR GFTGA BUULJ DXCCI VQPHQ SWKMY. What are these? To understand that, we need to consider them together with the letter itself... In particular, let's focus on the letters in bold. Aside from spelling 'fourth', they also:

appear in words immediately preceding some crossword-style clues to five-letter people, places and things:

f = Mr. Cameron, the former PM = DAVID

o = duck made of down = EIDER

u = creator of a logical principle = OCCAM

R = uses a die... maybe = ROLLS (or you might prefer to read this Wikipedia page if you don't understand why I linked to that just now...)

t = location of Mounts Vaea and Silisili = SAMOA

h = Dutch national flower = TULIP

Now look again at that 'PS' - what do you see? Notably, if you focus on the repeated letters within these words:

Each of the words we have just found in the crossword-style clues can map exactly to the nonsense words listed in the 'PS', as if by a substitution cipher:

RNEZR → DAVID | GFTGA → EIDER | BUULJ → OCCAM
DXCCI → ROLLS | VQPHQ → SAMOA | SWKMY → TULIP

Moreover, it has already been observed in the main post that every letter of the alphabet except 'O' is represented here. So it appear that we have found a 25-letter key for a substitution cipher...

ABCDEFGHIJKLMNOPQRSTUVWXYZ
ROLRVIEOSMLAIA-MADTDWSUOPI

Why else does this number ring a bell? Well, next look at the 5x5 grid. There are 25 squares here, so it's quite likely we will need to assign one letter to a space, and presumably find a way to read off a message. Is there a way to find a path through it?

Yes. The words 'must you' in the accompanying message - and the presence of black dots in the grid - should direct our attention to a MASYU grid-deduction puzzle. This has a fairly trivial unique solution:



So if we can work out the correct way to arrange the 25 letters of our substitution cipher across this grid (making use of that 'U', no doubt), we will likely be able to read off a message by following the solved masyu path.

However, at this point I have not yet been able to work out the correct arrangement for these 25 letters... It seems clear to me that with 25 letters, the trick is to arrange them throughout the grid itself - one letter per square - and then use the path to read a 22-letter message, rather than attempt to fit them along the path (which would be 3 letters short...). One to return to later...

What else do we have at our disposal? Well, the four semaphore flags spell out the letters NGLM (as mentioned in the puzzle text), but I cannot yet spot their significance. It may instead be the case that the exact letters are unimportant but the the flag positions for these letters are required to be positioned over the map of the US in some way to connect city dots, but I don't see it yet. For reference, the cities marked on that map look to me to be (starting at the top of the 'B' shape and proceeding clockwise):

Amarillo, TX
Wichita, KS
Springfield, MO
Memphis, TN
Jackson, MS
Montgomery, AL
Macon, GA
St Augustine?, FL
Tampa, FL
New Orleans, LA
Dallas, TX

Again, I am yet to spot their significance.

This is what I have so far. If we can resolve the intended letter path and reading of the cipher already identified, this will doubtless be a big help for the other steps of the puzzle...

Answer 2

UPDATED

The text following the bold letters seems to clue the following words:

David, Samoa, Tulip, Occam (credit Stiv), and Rolls

I am tempted to

Stick them in that box

But there is one too many words! So I got sucked into the cipher trail... but it led to dead ends. Then I tried using the flags but that went nowhere good. But...

TULIP goes in the 4th row, that seems obvious. Only one word has a U ("fits one way")

Now we see

The blockquoted letter has paragraphs beginning with S (So), D (Don't), O (Of), T (There's), and E (Eh). We can use this to get the order of the words in the box.

The result:

SAMOA
DAVID
OCCAM
TULIP
EIDER

Next, let's look at the dots.

The dots fall on O,V,E,R. Spells over. Over what? Over where? No idea. If you turn the map or flags over, you get an upside-down map or flags. If you turn the square over, the dots now fall on 'S,A,L,I', which when combined with the missing A in sem(a)phore makes ALIAS, which is interesting but probably useless.

So what does it mean? How to bring in the map and flags? No idea.