Meantime in Gondolin, the city had become a powerful point in the war against Morgoth. But this very fact had made some very nervous. Some think that this would make the city more of a target for Morgoth and indeed there was some signs that Morgoth was increasing his attacks upon it's territory. The leaders of the West decide that the city could host a large number of explosive missiles which would be aimed at Morgoth's armies. Now, Morgoth had developed similar missiles of his own and some of the population were very nervous at the prospect of so much fire-power in the city. One of those was the King's daughter, Idril. One day, a young man, Tuor enters the city, fleeing from the slave-pits of Angband. He has evidence that the city was indeed in Morgoth's mind and that the Lord of Angband was planning an assault upon it.
Tour was a young man who had suffered much at the hands of slavers in Angband. But coming to the city of Gondolin he was received as an escaped hero and welcomed by all in that fair city. Even so by Idril, daughter of the King, Turgon. In fact, he and Idril have meetings together, romantic times and they fall in love. This is partly due to the fact that Idril knows that she is admired by Maeglin the King's sister-son and there was just something about that son of a dark-elf she didn't like and was glad of an alternative. Idril was fair, beautiful, wise and loved by all in Gondolin. Despite some misgivings by some over the presence of mighty weapons near the city, there was at these times a lull in the wars between the West and Morgoth. In this peace, the love between Tuor and Idril blossoms. They were wedded in a fair ceremony in the city with the approval of the King and all in Gondolin. Save Maeglin who hid u pleasant thoughts, but seen the popularity of the wedded pair, he kept these to himself. They bore a son, Earendil the mightiest mariner of the seas. The people of the city were glad whenever the pair were in their presence.
Maeglin had become popular with the Men of Brethil. He pesuaded a large army of them to station at Gondolin. This has the effect of making the city appear very warlike. Tuor undertakes a mission to Angband territories were he discovers that Morgoth is indeed mustering a large army though it's target isn't clear but some think it could be Gondolin. Turgon is informed of this but had become proud and thinks that Gondolin under the protection of the western armies will not be penetrated.
Then there came the night of horror. On one evening the Sun set in a sky of red. Out of the North from Angband came seven missiles aimed at Gondolin. This created rivers of death and fire in the city. Then there came the long-prepared army of Morgoth. This army was strong enough to push back the allies beyond Gondolin. The city is cut of by Morgoth's forces and aid cannot come to it. Surrounded by a stronger force it withstands a bitter siege. The force of Morgoth contains Trolls, Balrogs and Dragons. Heroically though they are defended by Glorfindel, Tour and even Maeglin, the gates of the city are broken at last. The city falls and the fall of Turgon is with it's ruin.
In the wreck, Maeglin sought Idril and attempted to take her by force. Tuor finds him and confronts Maeglin and throws Maeglin over the walls of Gondolin to his death. Tuor and Idril lead a very few survivors of the attack out of the city via a secret tunnel. However, in there retreat, the refugees encounter a Balrog in the mountains. The Balrog is confronted by Glorfindel and both slay each other. The refugees are aided by the Eagles of the mountains that cover them in their flight. The survivors settle in the reeds of Sirion with those of Doriath were an Elven country does rise of sorts. But Idril and Tuor are sickened by the slaughter of the world. They build a ship and set sail to the seas in a red sunset and are never seen by any again.