Twelve short lines, and the whole poem is a held breath followed by a gasp. Browning gives us three bleak scenes, a barren bank, a glowering sky and a walled-in world, and rescues each with the same hinge-word, "Till". Only in the last line do we learn what the rescues were leading to: "That was thy face!"
The first two stanzas read like nature poetry. A "starved bank of moss" is crossed by a flash of blue, and the flash turns out to be violets. The colour arrives before the flower: "Blue ran the flash across." "Ran" and "flash" make the blossoms sound like a spark, something that happens in an instant rather than something that grows. Then the image becomes a birth, "Violets were born!" Because the moss was "starved", the flowers feel less like decoration than like hunger answered. The second stanza looks upward. The sky wears "a scowl of cloud", a personification that quietly anticipates the human face at the end. The cloud is also a "shroud", a word for the dead, and the light does not simply shine through it but "split" it, "ray on ray", as if the darkness had to be broken open. The reward is saved for the end of the line, with the adjective leaping ahead of its noun: "Splendid, a star!"
The third stanza changes the scale and the kind of trouble. "World" is the biggest word yet, and the problem is no longer weather but something closer to imprisonment: it "walled about / Life with disgrace". The poem never says what the disgrace is, and that is wise, because we only need to feel the walls. The relief is "God's own smile came out", and "came out" borrows the language of the sun emerging from cloud, so the divine smile is still described as a kind of weather. Then comes the swerve into the second person. The violets and the star turn out to have been previews, and the person addressed outshines them. The speaker says outright that a face did for his life what spring and starlight do for the world.
The form carries this feeling of release. Each stanza rhymes abab, and the lines alternate between a longer one of about three beats and a shorter one of about two. The long line sets up the gloom and the short one snaps the surprise into place: "Till, that May-morn" is followed by "Violets were born!" The rhymes close like latches: born and morn, far and star, and finally disgrace and face. That last pairing sets the wound and the cure side by side, so the ear hears the face answer the disgrace. The exclamation marks at the end of every stanza make the pattern clear, and the openings "Sky--what a scowl" and "World--how it walled" have the sound of someone bursting out mid-thought. The vocabulary is plain, almost all one-syllable words, so the few longer ones, "violets", "splendid" and "disgrace", stand out.
Browning is best known for long dramatic monologues, in which speakers reveal themselves at length. This poem does the opposite. In a dozen lines it gets its force from repetition and a final break in the pattern. Two stanzas teach us to expect a natural wonder, and the third gives us a person. The title adds a last twist. "Apparitions" usually suggests ghosts, but here the word is reclaimed for things that appear suddenly and make life bearable. The poem is not sentimental, because every miracle begins in real deprivation: starvation, a shroud, a wall. Love matters here because it arrives where the darkness was longest, and the poem lets us feel that darkness before it lets us see the face.