The title does a lot of quiet work here. An expatriate is someone living outside their home country, and the speaker's situation shows up in small, ordinary moments rather than in any big statement. He stares at a wall until his vision blurs and the wall doubles, which suggests a mind drifting, idle or unmoored. Then he hears neighbors talking in a backyard he can't see. The language is English, yet he can't quite follow it. That detail is odd and a little unsettling: even the familiar-sounding words have become slippery, as if distance has made his own language foreign.
The final image, a snail pushing out of its shell with its eye-stalks reaching in two directions, answers the doubled wall. The snail is a creature that carries its home with it, and it also looks two ways at once. The poem doesn't say what the speaker feels, but the mood is quiet, watchful and a little lonely, with a gentle curiosity at the end.