The speaker watches a friend whose life has been slowly emptied out by drugs, and the poem uses the ellipsis as its main image. Every "because" he gives for his pain trails off into dots, the way the weed in high school gave way to pills and empty bottles. What's left is a series of gaps: silence, "nothing left over by nothing," holes in the brain and in memory. His vocabulary and wits, the speaker says, have been dulled by self-medication.
The speaker doesn't try to fix anything. They sit in the backseat of his car, watching "from afar," aware that both of them are covering for their own silences. The mood is sad but quiet, almost numb. Near the end, the loud grindcore from the stereo oddly makes room for stillness. For a moment the speaker feels they understand how silence is possible, which suggests a sort of closeness with the friend, even though they can't fully reach him ("wishing abstractly that I could be all there").