Eight short lines carry a whole day's misbehaviour, and the poem never raises its voice. A man shouts at the fields, paces, smashes some windows and goes home. The title, "Alter ego", tells us who he is: the speaker's other self, the one who does what the speaker would not. The central idea is that we know our doubles intimately even as we keep them at arm's length. The poem's structure carries that tension.
The four actions run in plain, unbracketed lines: "he shouted at the fields", "walked up and down", "broke Barebone's windows", "and went home". The speaker's comments are tucked into parentheses, so the rowdy self gets the open lines while the observing self whispers from inside brackets. It is as if the respectable half of a person can only comment on the wilder half in an undertone. Yet the brackets also work like a leash or a hand over the mouth, an attempt to contain something that keeps spilling over.
Each parenthesis gives the double a different name, and the names move closer. "The crooked fellow" is a human at a slight distance, a bit bent, a bit shifty, and the phrase may faintly recall a nursery-rhyme figure, though that is an inference, not something the poem states. "The churchyard cock" is a bird, vain and noisy, strutting among the graves. The word "cock" suggests both a rooster's swagger and a rooster's early-morning crowing, which fits the opening "In the morning". Then comes "my dog-brother", the only phrase with a possessive, and the last word the poem gives us. The sequence moves down from man to bird to dog, and it moves in from "he" to "my". By the end the speaker has stopped treating the figure as a stranger and claims him as kin. The hyphenated "dog-brother" is both affectionate and a little rueful: he is a creature of instinct, but he is family.
The action follows its own curve. Shouting at fields is almost comic, since fields cannot answer, and the outburst has no real audience. Walking "up and down" is a restless animal's pacing. Then the violence lands on something specific, "Barebone's windows". It is the poem's only proper name, and the poem gives no context for it. The name has an austere ring, as if the windows belonged to someone stiff or respectable, but that is an impression, not something the text confirms. What matters is that the rage moves from empty landscape to a person's property. Then the final action is the flattest one: "and went home". After the breakage, the deflation is nearly domestic, with no punishment, no remorse and no explanation.
The sound of the poem supports this. Almost no line is longer than four or five syllables, so the poem moves in short, clipped steps. Hard consonants gather in the middle: "crooked", "cock", "broke", "Barebone's". They click and snap like the glass itself, while the first and last actions are smooth, mostly soft syllables ("shouted at the fields", "went home"). There is no rhyme, and none is needed. The poem has no full stop either, so it ends with the parenthesis and the thought stays open, as if the speaker expects the double to be out again tomorrow.
What makes the poem worth reading is its restraint. A heavier poem would diagnose the anger, apologise for it or glamorise it. This one just reports, then adds three nicknames, the way you might talk about a sibling who is embarrassing and impossible to disown. The tone is amused and tender, and a little nervous. It suggests that the self-knowledge we tend to dread, admitting the part of us that shouts and breaks things, can be handled with a shrug and an affectionate name.
For a poem of fewer than thirty words, that is a lot to hold. It shows that a poem can say something true about a divided self without a single abstract term, using only a handful of verbs, a few animal names and some well-placed brackets.