Late at night, the speaker goes to bed, but not with his wife. Instead, his past gets in beside him. The phrase "in lieu of my wife" is the heart of it: something has taken her place. The poem never says why she is absent, and that silence matters. She might be gone, dead, or simply elsewhere, but we only know that the bed holds memories where she should be.
The second stanza moves from the bed to the nights themselves, which have grown "longer than I / can sleep." The speaker lies awake with nothing to do but remember. The line break after "I" leaves him briefly hanging, a small echo of the loneliness he describes.
The mood is quiet, tired, and sad. Nothing is dramatic or loudly mourned. The plain language and short lines feel like the speaker's own flat, worn-out voice, which makes the feeling of loss seem steady and ordinary, something he lives with night after night.