The title does a lot of work here. We never learn who has died, but "Widower" tells us the speaker is a man whose wife is gone, and the three short lines show how he lives with that. He goes down into the cellar with a cane, which suggests he is old or unsteady. Then comes the quiet confession: he talks to her things.
The poem doesn't say what those things are. Judging by the setting, they might be boxes, tools, jars, or clothes left in storage. What matters is that he speaks to objects because they are all that remain of her. The dash and the plain, almost casual phrasing make the admission feel private, as if he half expects to be judged for it.
The mood is gentle, lonely, and a little sad, but not dramatic. The cellar, a low and hidden place, suits his grief. He isn't crying out; he's simply carrying on a conversation that no longer has anyone to answer it.