The speaker notices a boy standing alone in a dark corner, headphones on, lost in a song only he understands. He is physically close, yet he seems miles away. The speaker recognises the look on his face right away, because it's one they see every day: the look of someone who is surrounded by people but never really seen by them.
At first the poem reads like quiet observation, even gentle concern. The speaker wants to see him smile and wishes they could hear what he has to say. Then the last two lines turn everything around. What bothers the speaker most is the reflection in their own mirror. The boy's loneliness is their own.
The mood is hushed, sad, and a little tender. There's sympathy for the stranger, but also a private ache, since the speaker seems to be reaching out to someone they can't reach in themselves.