Treasure Train and Between The Trees
My new theory is that the Ghost EP is hidden on one or several trains, I would guess probably one on every continent.
The first clue to this idea came from the song Desperate Living, it sounds like a train track is being built, "A play folds out on the forest floor", "Building bridges and statues", "Listen breakers and listen bucks, these are the one-rail hooks". I imagine this somehow takes place before the events of Treasure Train, "I bought a one way ticket back to July".
And he describes and mentions the ghost, "Quantum theory, breathless yet... dis-corporate", "We are hostages, held for ransom by a gentleman ghost".
In Treasure Train he says "but there's a small window at the end of this train i HEAR something out there", what he is hearing is the "swan song" that is mentioned in Between The Trees, "Radio, radio, can you hear my swan song?". But more interesting is both songs mention a doctor, in Treasure Train he says "I'm the physician, this medicine will keep me alive", then in Between The Trees he says "Doctor, doctor, what's my status? Will I stand or will I fall?".
The character in Between The Trees is the ghost, "I can stand here blankly, I can hold my breath, I can even not exist at all". And I'm guessing the "swan song" is one of the songs in the Ghost EP.
The the line in Between The Trees "There's something of me out there in between the trees but I don't believe I can give the thought the time" is a connection to the line in Treasure Train "I hear something out there, I didn't know and I wouldn't try I didn't have the need".
This all reminds me of the demo song The Greatest Weight, which says:
"And say to you, "Everything unutterably small or great in this life will have to return to you
All in the same succession and sequence, even this spider and this moonlight BETWEEN THE TREES, and even this moment and I myself - the eternal hourglass."
Particularly the phrase "the same succession and sequence", could describe a train that always comes back around, perhaps in "28 days, 6 hours, 42 minutes, 12 seconds".
There is also a really interesting quote from the Earth Tour book that seems to fit this idea. Erik is talking about how dumb it is to compare new life experiences to movies that we've seen... and then says "You can either be an 'idiot', a local phenomenon that is no more than a necessary product of your location, or this less limited, yet less identifiable phantom being, with nothing concrete to tie you to anything. No home gives rise to no beliefs... No time to slowly get involved in some local absurdity confused with 'purpose' or 'necessity'. There was something disturbing about seeing myself for what I really am, and how little I have to do with it." The bold text seems to describe a ghost that is constantly travelling rather than lingering in one place.