The title suggests that the poet wants some answers, like Job in the Bible who lost his children and demands an audience with God. The poet also references religious vocabulary, especially in "The Lost Garden," so one way of understanding the collection is that it is the questions a bereaved father might have for the fate-maker, asked from his own location in time, middle age, or Noon. That is suggested also by the title of "Summer Storm," which frames the speaker in the middle of the year.
Broadly speaking, the poetry is about the death of his child, but actually, a better analysis would be to say that the poetry is about the way that experiencing the death of his child at a young age reoriented the poet so that through time, they are forced to encounter "normal life" from the broken, experienced position of a bereaved father. For instance, when children in his life reach twenty-one, he remembers his own child who might have been that age, becoming an adult. This is a complicated idea that goes beyond simple mourning. He is asking about the mystery of existence, because some people get more of it than others.
But what would it matter unless humans died? Because of human death, the passage of time takes on the feeling of a crisis, because the poet wants to spend their time happy, of course, but in reality, it takes time to mourn the loss of his child, and beyond that, the loss gave him insight into a kind of experience that is always happening all around him (explored through imagery and symbolism). So in a way, he has found an alternative to happiness. He lives in pursuit of peace, not happiness, because if he can be calm and collected, he observes an intriguing reality with a unique insight.
