Five lines, one sentence, and not a single clue about who "you" might be. Gabriel Armentrout's «I Shall Miss You Most...» opens with a plain confession and then spends the rest of its length looking at a marsh. The feeling is stated once, in the first line, and everything after that is landscape asked to carry the weight.
The central idea is that longing has its own hours and its own weather. "Most" is the quiet key word of the opening line. It admits that the speaker misses this person at other times too, and that dusk is simply when the ache is sharpest. The future tense of "shall" adds to the mystery. It could be a promise made before a parting, or a prediction of how the speaker will feel afterwards, and the poem never settles which. It is stronger for leaving the question open.
The imagery is built with care. Twilight "brings the rising mist / To hang upon the reeds", and the verbs matter: the mist rises, then hangs. It is movement that stalls, something lifting and then clinging to thin stems, which is a fair picture of a feeling that won't clear. (The text supplied reads "risising", which I have taken as a slip for "rising", the reading the rhythm supports.) The next line bends its grammar in an interesting way: "the evening darkens cold". We might expect "dark and cold" as two separate facts, but here cold comes attached to the darkening itself, so the dusk is felt on the skin as well as seen.
That small shift points to something larger. The poem moves from sight (twilight, mist, reeds) to touch (cold) and finally to hearing: "Mallards' cries across the marsh". As the light goes, the eyes are no longer much use and sound takes over, which suits a poem about someone who cannot be seen. "Cries" is an ordinary word for bird calls, but it is also what people do in grief, so the marsh seems to voice what the speaker leaves unsaid. "Across" suggests distance, a call travelling over open ground with no certain answer. The poem never draws that comparison, but the imagery invites it.
Sound does quiet work as well. The letter m hums through the poem: "miss", "most", "mist", "Mallards'", "marsh". It starts with the speaker's own words and ends in the last word of the landscape, as though the place were echoing the feeling. "Marsh" closes on a soft, hushed "sh" that lets the line fade rather than ring.
The form follows the same logic. There is no rhyme, so "reeds", "cold" and "marsh" never click together, and the poem never gets the small satisfaction of a closing chime. The rhythm is loosely iambic. The first line is short and heavy, with "shall", "miss" and "most" all demanding stress, like three slow footsteps. The longer lines then glide: "When TWIlight BRINGS the RIsing MIST" and "With MALlards' CRIES aCROSS the MARSH" each run to eight syllables. Between them, "To hang upon the reeds" is shorter by two syllables, and the line itself seems to hang. As printed here, the poem has no commas and no full stop, and the title already trails off in an ellipsis. The "when" clause runs on until the lines simply stop, so the sentence is never closed.
Notice, too, what disappears. "You" appears once, in the first line, and never returns. By the end only the place is left (mist, reeds, birds, marsh), which enacts absence structurally as well as describing it.
What makes the poem worth reading is that restraint. It does not explain the loss, name the person, or tell us how to feel. It picks one moment, the hour when light drains from open ground, and trusts the reader to supply the rest. For a student, it is a useful lesson in how a poem can say a great deal by saying very little, and how the right sounds and the right hour can do the work of explanation.