The letter is "written" by pasting words cut from newspapers and magazines on what appear to be fast-food wrappers.
Do not read this under an open sky! Or when anyone you don't know is in sight. Or while not wearing your aluminum foil hat. This last is the most important! Without your foil hat they will know your thoughts!
I have discovered their secret! Not only do the walls have ears and the ceiling have eyes and the waiter is an agent in disguise, but they are planning to use elevator music to reprogram everyone's brain using elevator music (you didn't think it's because anyone thinks it sounds good, did you?). You must come help me stop them before it's too late. I will know you by your shining foil hats and clear, unclouded eyes -- you will know me by the same. Everyone else here's mind has been corrupted by them. Come soon! Bring large amounts of aluminum foil and duct tape!
I will bury this message under my kitchen floor, so it will reach you without interference.
Yours in the struggle,
(Name withheld for security reasons)
This second, attached message is typed neatly on business-grade paper. It is not signed.
Dear Agents of the Floating Temple,
Please do not worry about your message from poor (name withheld for security reasons). He or she is quite unwell and needs a long period of undisturbed bed-rest, without any disturbing visitors. And aluminum foil is now illegal here.