I think this song is talking about spirits making their way to heaven, or some spirits that don't deserve to be in heaven and are still trying to make their way there.
"There are ghosts in here
They are stuck in the middle"
They're stuck in the middle being purgatory.
"Heading straight for the heavens
But explode on the way"
They don't make it straight through.
"Just like dominoes
First one, then come the others
Long invisible lines
Restless prisoners"
There are many spirits, lined up, waiting to be accepted into heaven but they are stuck and jailed in purgatory.
I think this song is talking about spirits making their way to heaven, or some spirits that don't deserve to be in heaven and are still trying to make their way there.
"There are ghosts in here They are stuck in the middle"
They're stuck in the middle being purgatory.
"Heading straight for the heavens But explode on the way"
They don't make it straight through.
"Just like dominoes First one, then come the others Long invisible lines Restless prisoners"
There are many spirits, lined up, waiting to be accepted into heaven but they are stuck and jailed in purgatory.