The poem watches a woman waiting for a husband who hasn't come home. The speaker never describes her feelings directly. Instead, the room does the talking: an unread letter, a pair of pearl ear-rings left on a cushion, an old brown-yellow map under glass on the table. Each detail hints at a story, though the poem never tells us what it is.
The opening lines are a little ironic. A bulge in her coat is said to show her husband's love, yet the anxiety on her face points to a gap between them. The map is the sharpest image. It cannot say where he is, so even a tool for finding places is useless here.
The mood is quiet, uneasy and lonely. By the final lines, evening settles in, and the light, which might comfort her, cannot cover the emptiness. The title, "Sleeping Light," seems to match that dim, drowsy, unresolved feeling.