It tells the story of a father who is carrying his sick son, while riding homewards after dark on horseback. The son is convinced that they are being pursued by the Erl-King, who speaks to him to persuade him to come away with him, while the father insists that the Erl-King doesn't exist — what he sees, so he tells the boy, are only trees, bushes and fog. Yet the boy will not be calmed, finally screaming that Erl-King is touching him. Even the father is horrified now, and rides the horse as fast as possible. When he arrives, he realizes that the boy is dead.
The poem was inspired by a Danish folk tale, which was translated to German as "Erlkönigs Tochter" ("Daughter of the Arlen King"). However Erlkönig is a mistranslation (by Johann Gottfried Herder) of the Danish "ellerkonge", which actually means "King of the elves" (that would be "Elfenkönig" in German, in case you wondered). It is possible that Goethe went with the "wrong" translation consciously, as the Erl-King does not fit in with what most people of the era would have recognized as an Elf-King; in the ballad, he seems to serve as a substitute to the Grim Reaper or Death. The "rational" interpretation is that the boy is hallucinating from fever.
"Erlkönig" is one the most recognizable of Goethe's works for Germans, thanks to its time-honored status as an inevitable school study medium. So is Zhukovsky's adaptation (see below) for Russians.
The poem was set to music (for solo voice and piano) by Franz Schubert in 1815. In Germany in the 20th century the word "Erlkönig" came to denote a car prototype on a nightly Autobahn test drive (speeding, like the father in the ballad, "through night and wind" and fog) in an attempt to evade photojournalists.
Schubert's "The Erl-King" had various other adaptations on its own, including a piano-only version by Franz Liszt, and a famous violin rendition by Heinrich Wilhelm Ernst, which is considered one of the most technically difficult solo violin pieces of all times, if not the most difficult. Ernst's version is notable for including identifiable individual parts and tone variations for the music accompaniment (which is played throughout), the father (in lower notes), the son (in high notes), and the Erl-King himself (in dulcid notes).
A rhyming translation can be found on Wikisource.
"Erl-King" provides examples of the following tropes:
- Death of a Child: The poem is about a farmer riding furiously through the night to get his sick son home. The feverish young boy becomes increasingly distraught, claiming that the Elf King is trying to take him. Whether the Elf King is really there and trying to kidnap the boy or if it's just a fever hallucination is left ambiguous, but by the time the father reaches their home the boy has died.
- Died in Your Arms Tonight: The last line of the poem: "In his arms, the child was dead."
- Downer Ending: By the time the father arrives home, his son has already died.
- The Fair Folk: The Erlking and his daughters.
- Faux Affably Evil: The Erlking shows his real face after his seductive approach doesn't work on the boy.
- Hell Is That Noise: Schubert's adaptation of the ballad is notable for the agonizing cries of the child, who horrified, implores his father to see the Erl-King approaching.
- Imaginary Enemy: The boy feels he is pursued by a supernatural entity which his father cannot see, and which wants to take him away to a supernatural realm against his will.
- It's Probably Nothing: The father repeatedly insists that what the boy sees and hears are from mundane sources, e.g. a tree or the wind.
- Maybe Magic, Maybe Mundane: The poem does not answer the question whether the Erlking is real or only the dying boy's fever dream.
- Nameless Narrative: The father and his son are not named.
- Not Now, Kiddo: How the father initially disregards the boy's fears.
- Not-So-Imaginary Friend: The father believes the Erlking is only a figment of the boy's imagination and keeps telling his son he does not exist, but by the end he "feels a horror" (dem Vater grausets), which indicates he (and with him, the reader) is left wondering whether the Erlking is real, after all.
- Supernatural-Proof Father: The father repeatedly insists that what his son claims to be visions of the Erlking are just streaks of fog, willow trees, and so forth. But when the boy claims that the Erlking has moved from trying to entice him away to trying to abduct him by force, even the father seems uncertain as to whether or not his son is simply hallucinating.
- Touch of Death: Played with. At the end of the ballad, the boy cries in horror stating that the Erl-King got a hold of him. By the next two stanzas, the boy is dead. The other possibility, of course, is that the boy may have succumbed to his ailment.
- Would Hurt a Child: The Erlking offers violence against the boy.