Heaney's poem is about the death of his younger brother but told from the perspective of the poet, who must return home for the funeral. The poem is written in such a way that the identity (and age) of the person killed is not made clear until the end of the poem.
The first stanza places the poet at college, waiting to be taken home, not by his parents but the "neighbors," the first sign that something unusual has happened. Of special interest is the second line, with its irregular stresses suggesting the sound of the bells marking time. It's clear that this waiting is both boring and a time when the poet must be thinking about what he is about to face.
The second stanza begins with the poet meeting his father crying and the sense (in the second line) that this is unusual, since "he had always taken funerals in his stride." This is a kind of inversion of roles and suggests that the poet, although just a college student, is expected to be emotionally strong. It is as if the crisis has elevated him to manhood, worthy of being addressed by "Big Jim Evans."
The detail about the baby laughing at the start of the third stanza is both incongruous and suggests something about the poet's family and his embarrassment at being greeted by the old men. On the one hand, he is embarrassed by his sudden standing as an adult, but on the other, it is possible that being the adult sibling of an infant is another cause of embarrassment.
This sense of embarrassment continues into the next stanza, where the adults offer empty condolences and he is officially identified by "whispers" that he is "the eldest / Away at school," fixing his position in the family and his social status (as a college student). It is awkward that these strangers know about his situation, but more awkward is this performance required of him of public grieving, represented by his mother holding his hand.
The emptiness of this occasion is suggested, in the next stanza, by his mother's "angry tearless sighs," a kind of emotional repression that leads us to wonder why the father would be crying over his dead child, but not the mother. The mother's emotional distance is reflected in the dull fact of the ambulance arriving ("at ten o'clock") with the corpse.
The next six lines represent a shift, both in time (it is "Next morning") and tone. The poet visits the corpse of his dead brother alone, the room "soothed" with candles and flowers. This sense of peace is perhaps at odds with the usual commotion of the house. Heaney concentrates on visual details: it is "the first time in six weeks" he has seen him; he is pale, with a red "poppy bruise" on his "left temple," otherwise apparently unharmed. He was hit by a car, we infer, since "the bumper knocked him clear." This concentration on visual detail stands in contrast to any sort of emotional response we might expect from the poet. In fact, the observations here have a detached, clinical quality that seem to require explanation.
The final line of the poem is devastating and brilliant. It begins with another statement of fact: the coffin is four feet long, but ends with an observation that crystalizes the conflicted feelings of the poet—"a foot for every year." The brother was only four when he died; his death in a car accident was meaningless and random; there is a suggestion that his parents, in continuing to have children, are unable to provide enough attention and that the lives of children are cheap. Like his mother's repressed anger, the final line simply relates the facts about the death of his brother, but in doing so he evokes a unspoken sense of rage and hopelessness.