The speaker of the poem and his family have just experienced a truly appalling tragedy. The speaker's four-year-old brother has just been knocked down and killed by a car. In keeping with the tradition of Irish rural communities, the boy's little body has been laid out in a room where people gather to pay their respects.

The speaker observes that his dead brother is "Wearing a poppy bruise on his left temple." The temple is located on the side of the head, between the forehead and the ear. There are two of them, a right and a left temple, and it is on the dead boy's left temple that a large bruise can be observed.

It is clear that this bruise was sustained in his fatal accident. According to the information given to us by the speaker, it seems that it was a collision with the car's bumper that killed the boy. That would account for why his body has no "gaudy scars," just a bruise on the head.

To the speaker, the bruise on his brother's head looks like a poppy. Though most people think of poppies as being red, there are in fact purple poppies, and it's one of them that the dead boy's head wound resembles as he lies there.