The speaker feels unwanted and is convinced the people around them are quietly irritated by their presence. Nobody actually says anything cruel. Instead, the speaker "hears" the silence, imagines the insults ("You're nothing but a plague"), and reads frustration in the faces and voices nearby. When others insist "It has nothing to do with you," the speaker doesn't believe it and repeats "Lies lies lies."
The mood is sad, anxious, and lonely. The speaker is afraid to ask what's wrong, comparing the question to opening Pandora's box, because the answer might confirm their worst fear. The poem suggests a mind that fills the gaps with self-blame, and it's unclear whether the others really feel this way or the speaker is assuming it. The short, plain lines make the pain feel raw and direct. The ending, "I guess it's about time I leave...", trails off with the ellipsis, leaving a quiet, worrying sense of resignation and withdrawal.