Death arrives in this sonnet as one long, postponed sentence. For eight lines the speaker stacks up clauses beginning with "When": when the heart withers, when the eyes stop weeping, when the earth receives the head. The main verbs keep being put off, the way people put off thinking about the thing itself. The picture she builds is grand and consoling. There is a "gloomy mansion of the dead," Envy turning away to shed a tear, and poets keeping vigil at her grave. It is a fantasy of being mourned beautifully. The final line demolishes it.
The imagery of the opening is physical and unsparing. The heart is "with'ring," the form "faded," as if the speaker were a plant going out of season. Temperature does the rest. The "fev'rish head" of a woman consumed by feeling is received by "earth's cold lap," and the word *lap* turns the grave into a grim parody of a mother's embrace. The "freezing bed" a few lines later finishes the thought: death is the cooling of a long fever. Water runs under the poem too. The eyes that "cease to weep" in line three have their answer in the sestet, where the breast will "bathe in endless rapture." Tears become bliss. The poem lets her imagine that exchange before taking it away.
The form helps this along. The octave is Petrarchan, rhyming ABBAABBA on only two sounds: *dead, head, shed, bed* and *sleep, weep, sweep, keep*. The effect is of a tolling bell, with the same few sounds coming back as if the speaker cannot escape them. The sestet moves to alternating rhymes (*shore, care, more, there, deplore, share*), which feels lighter and more hopeful. The "Then" that opens line nine finally answers the "When" of line one, and the pale ghost smiles on the "Elysian shore," "releas'd from ev'ry mortal care." The meter is steady iambic pentameter throughout, with elisions like *with'ring*, *fev'rish* and *th'* squeezing the words into shape. That steadiness makes the break in line thirteen audible. "Ah! no!" puts two heavy stresses side by side and stops the line's smooth stride.
What follows is a reversal the rhymes have been preparing. In line eleven she imagines being freed "to repine no more," and two lines later the same sound returns in "deplore," so the promise is undone by its own rhyme. The restless shade also contradicts the very first idea of the poem, since the heart was supposed to "sleep." Most cleverly, the last line ends on *share*, which belongs to the *care / there / share* rhyme chain. The hoped-for place ("there") and the freedom from "care" are tied by sound to the one thing missing. Paradise is measured by whether Phaon is in it, and he is not.
That name matters. Phaon calls up the classical legend of Sappho and the ferryman she loved, so the speaker seems to be speaking in a Sappho-like voice, though the poem never says so outright. The title's numbering, "Sonnet XXXVII," also suggests one piece of a longer sequence. Judging by this sonnet alone, the sequence is about love as an unfinished condition, not a story with an ending. The poem stops mid-argument, with no consolation reached.
There is another, quieter tension in the octave. Time's "obliterating pinions sweep / The spot" where poets will gather, so the grave is to be both visited and erased. The speaker wants to be remembered and knows she will be forgotten. That is a poet's anxiety, and it makes the speaker more self-aware than the conventional stock phrases (*pinions*, *vigils*, *Elysian*) might first suggest. She is composing her own elegy while doubting it.
The sonnet matters because it refuses the comfort it builds. It borrows the usual afterlife of ghosts and shores and then declares it worthless without the beloved. The sonnet form supplies a turn, and here the turn is a kind of honesty. She would rather keep her grief than accept a heaven that has forgotten him.