Lines 1-8 Summary

Get out the microscope, because we’re going through this poem line-by-line.

Tonight my brother, in heavy boots, is walking
through bare rooms over my head,
opening and closing doors.

Our speaker hears his brother clomping around the house on a floor above him.
The mention of the heavy boots sounds kind of ominous, right? Especially since we started with an already-ominous title, "This Hour and What Is Dead." At the very least, those boots are out of place in a quiet house at night.
What is his brother doing up there, anyway? Especially if the rooms are "bare"? And what's with all the opening and closing of doors?
It's an open opening. This poem could go in just about any direction.

What could he be looking for in an empty house?

Our speaker wonders at the motivations of his brother, what he could be searching for. But he also seems to be wondering what we're wondering. He's asking us a question, after all.
For our part, we're wondering why the house is empty. Is someone moving out or in? What's going on? Is the brother even there? How can a house be empty with people in it? So many questions, so few answers.
The spookiness in the title is reinforced by the emptiness of the house and this mystery of his brother's actions.

What could he possibly need there in heaven?

Wait a second. Our speaker's brother is dead? Oh. Well that explains it.
Apparently, the whole upstairs business is really just a metaphor for heaven, where the speaker's brother now is.
We get the feeling that maybe the real scene is more like this: our speaker, awake late at night, listens to the typical creaks and groans of the house, and thinks of his brother. He imagines those sounds to be his brother shuffling around above him.
Clearly there's a strong connection between these brothers. Even though the speaker's brother is dead, the speaker imagines him very much alive, and even in the same house. How sad.
For our speaker, it's a thin line between memory and imagination. He remembers his brother, and knows he's gone. But he also imagines him to be present, too.

Does he remember his earth, his birthplace set to torches?

Our speaker asks if his dead brother remembers the earth, his birthplace, which was burned.
"Birthplace" could refer to the whole earth or to the actual place where his brother was born, but, without any other information, we're going to assume it refers to the whole earth.
Of course assuming this raises the question: what would it mean if the earth has been set to torches?
We're guessing that the "set to torches" can work metaphorically in a couple of ways:
First, it might signify the emotional intensity of our speaker's experience, here in the living world. In other words, his brother's death could fill the world with the burning intensity of loss.
Second, it could refer to the fact that, now dead, the brother can never return to the earth, as you can never move back into a house if it has been burned down.
Still, because of the ambiguous way that this line is phrased, we can't completely avoid the hint that maybe there was a real event in the past: maybe the house where his brother was born was actually burned down, or the country in which he was born is in turmoil. We don't have enough information to even begin to piece things together, but that hint of a family trauma lingers in the background of the poem.

His love for me feels like spilled water
running back to its vessel.

The speaker compares the feeling of his brother's love to spilled water running back into its container using a simile.
It's a cool image, huh? Like watching a spill on rewind – the water rolling back into the cup, the cup standing upright again.
Okay, that's great and all, but what exactly does this image mean in terms of the poem?
For one thing, it suggests restoration. A unity (between the cup and the water) that had once been lost has now been brought back.
Plus, check out the word choice here. The use of "vessel," instead of a word like "cup" or "glass," also suggests that the experience, or remembering, or imagining his brother's love might be like bringing his brother (briefly) back to life. After all, death could be described as the spirit/soul being spilled from its vessel (the body). (We know, we're pretty deep sometimes.)
This simile might also suggest that the love feels impossible in a way, or at least not logical. After all, in this world, spilled water doesn't generally run back into its vessel. Come on, we wouldn't have so many paper towel commercials if we could just unspill things, would we?