Right before sunset, the speaker watches long bars of shadow stretch across the lawn toward the house. The line breaks slow everything down: "but / not / quite / yet" makes the shadows seem to hold back, hovering just short of the walls before the sun takes its power away over the mountains.
The second stanza is about how the same sight can feel completely different. Sometimes the shadows are lovely, a new way of showing off the light. Other times they look like fingers grasping, and they stand in for scary thoughts reaching toward the speaker's mind. The title, "It Depends On What You See," points to this: the shadows stay the same, but the speaker's mood changes what they mean.
The ending is quietly revealing. On the eerie evenings, the speaker closes the curtains and tells her husband it's "already so dark out." She blames the hour, though the poem suggests the real trouble is inside her. The mood is calm on the surface, with an uneasy feeling underneath.