The Fall of Gondolin is the result of the clash between the two most powerful forces in the world: the fallen God Morgoth, who represents ultimate evil, and the God Ulmo, the Lord of Waters.

The beautiful Gondolin is the city founded by the Noldorin Elves in a hidden and inaccessible location, so that Morgoth cannot find them.

Ulmo instructs a Man, Tuor, to go to the hidden city and deliver a message to its king, Turgon, that he must confront Morgoth if he wants to be rid of him. Tuor embarks on the difficult journey to Gondolin. Upon arrival, he delivers the message to Turgon, who refuses to leave the city and confront Morgoth.

This refusal has terrible consequences. Morgoth organizes a devastating attack on the city and, although the resistance of its defenders is epic, it does not prevent its capture and plundering. Tuor and the surviving Elves take refuge in the mountains, from where they watch in despair the destruction of their burning city.

The Fall of Gondolin was, according to J.R.R. Tolkien, "the first real story of this imaginary world," which, along with Beren and Lúthien and The Children of Húrin, he considered the three Great Tales of the Elder Days.