Two girls stay up late, talking the way close friends do, and they plan everything except the one thing that will actually happen. Dickinson's poem is a small story about confidence and its sudden correction. For three stanzas the speaker and her friend treat the future as a room they can furnish at will. In the last four lines Heaven overrules them.
The first stanza sets up the trap. "Fond, and late" compresses the whole mood of an intimate night into three words. Then the longest line in the poem, "We speculated fair, on every subject, but the Grave," runs on the way their talk must have, until the final "but" closes a door. The next line is clipped and slightly awkward: "Of ours, none affair." Death, they feel, is simply not their business. The poem is built around that omission.
The second stanza turns the girls into little rulers. They "handled Destinies, as cool," as though fate were a set of objects on a table, and they call themselves "Disposers." That word echoes the old saying that man proposes and God disposes, so the girls have taken over God's half of the job. God is demoted to "a Quiet Party / To our Authority." "Party" is a legal word, someone who signs an agreement, but it also suggests a guest at a gathering who sits politely in the corner. The humor is gentle and a little teasing, and it makes the ending hurt more. The girls are not arrogant so much as young, and the poem lets us enjoy their swagger before it takes it away.
In the third stanza the daydream turns inward. They dwell on "Ourself" in the singular, as if two friends had merged into one imagined future person. They picture growing up as something done to them, with girls "to Women, softly raised," as though lifted on a cushion. The dashes in "We -- occupy -- Degree --" slow the line into a ceremonial step, like someone taking a seat in a position already waiting for her. "Degree" suggests rank, an easy arrival at adult dignity with no struggle in it.
The form echoes this movement from ease to shock. The quatrains alternate longer and shorter lines, and the rhythm is loose and conversational, in the manner of Dickinson's hymn-like stanzas but with the regularity deliberately roughed up. Rhyme stays shy for most of the poem. The first stanza has none to speak of ("late" and "affair" barely touch), and the middle stanzas lean on soft pairings like "be" with "Authority" and "be" with "Degree." The cleanest rhyme comes at the very end, with "write" and "night." The promise to "cherish, and to write" is cancelled in the same sound that seals the poem.
That last stanza is where the word choice pays off. The girls part "with a contract," which carries on the legal language of "Party" and "Authority." Their agreement is private and heartfelt, but it is still a contract, and Heaven simply declines to honor it. The commas around "impossible" make the word land on its own. The poem never says what happened. Judging by the earlier mention of "the Grave," death is the likeliest reading, but Dickinson leaves it unspoken, and that restraint is more chilling than an explanation would be. "Before another night" also echoes "late" from the opening: one night is spent talking too long, and the next never comes. The "Quiet Party" turns out to have the last word after all.
The poem is significant for how much it does with so little. Dickinson's trademark dashes and capital letters mark the key words, "Girls," "Grave," "Destinies," "Heaven," so that the poem reads as a quiet contest of authorities, human and divine. It also manages a double tone, affectionate mockery of youthful certainty and real grief at its collapse, without ever raising its voice. And there is an irony in the poem's own existence. The contract promised letters, and Heaven made writing impossible, yet here is the writing, the poem itself, still keeping the friendship in words.