Waking should bring relief, but here it brings the worst moment of all. The speaker opens his eyes onto a darkness he can feel, and the poem never lets him out of it. Hopkins, a Jesuit priest, writes about a believer whose God has gone silent. His answer to what hell might be is unnerving in its simplicity: it is being stuck with yourself.
The first line sets the tone with the word "fell." In older English it can mean fierce or cruel, and it can also mean an animal's pelt. "The fell of dark" is therefore both savage and heavy, something draped over the skin. Darkness is not seen here but felt. The rhythm then slows the reader down. Hopkins builds lines around clusters of stressed syllables, and "What hours, O what black hours we have spent" has hardly an unstressed beat to rest on. The speaker addresses his own heart like a fellow prisoner ("what sights you, heart, saw; ways you went!"), and the semicolons and exclamation marks keep the voice jerking and pacing rather than flowing.
The octave keeps to a strict rhyme scheme, abba abba, and the rhymes feel like walls. "Day" in line one is answered by "delay" at the end of the quatrain, so light is rhymed with its postponement. Then comes a correction: "where I say / Hours I mean years, mean life." A bad night turns into a bad existence, and the poem's real subject appears. The lament that follows is "cries like dead letters sent / To dearest him that lives alas! away." Dead letters are mail that can never be delivered. Most readers take "him" to be God, and the details support that: the cries are prayers with no address to reach. The "alas!" wedged into the line sounds like a sob, and "lives... away" is worse than death, because he is alive but elsewhere.
The sestet turns from the night to the body, and from sight to taste. "I am gall, I am heartburn" has no "like" or "as" to soften it; the speaker simply is bitterness. Then comes the line that holds the poem's logic: "God's most deep decrees / Bitter would have me taste: my taste was me." The flavour he is made to taste is his own self. Hopkins pushes this inside the skeleton with a run of b sounds: "Bones built in me, flesh filled, blood brimmed the curse." The curse is not laid on him from outside; it fills him like liquid in a vessel. Here the rhymes loosen too. "Me," "see" and "be" echo each other while "decrees" only half chimes, as if the sonnet's discipline is fraying.
The last tercet gives the central image: "Selfyeast of spirit a dull dough sours." Yeast normally makes dough rise, but this yeast belongs to the dough itself, and what it produces is sourness. The spirit is both the ferment and the thing spoiled, so nothing external is needed. From this the speaker draws a frightening conclusion: "The lost are like this." The damned, he suggests, are punished by being their own torment, "their sweating selves, but worse." The poem's last word is "worse," and it rhymes with "curse" two lines earlier, so the ending closes on itself like a door.
What makes the poem significant is its refusal to console. The sonnet is traditionally a form for turning an argument toward resolution, and Hopkins bends it so that the turn leads deeper in. The poem is also unusually honest that faith and despair can live in the same mind, and that belief does not guarantee comfort. It makes that despair physical, with the tasted bile, the heartburn and the sour dough, so a reader can recognise it even without sharing the religious frame. Anyone who has lain awake while a night stretched into something much longer will know what "hours" meaning "years" feels like.