It was believed the Queen Gwynevere and Sir Launcelot were having an affair. Some knights planned to catch them, but the plan backfires of them. This created a lot turmoil between them. The king planned to burn the queen at the stake.
Sir Launcelot saved the queen and they fled for safety. After an intense war, the queen was returned to the king and Launcelot was banished from the realm.
Sir Gawain hates Sir Launcelot because he killed both of his brothers. Day after day he goes and tries fight Launcelot only to kill other knights. Finally they fight and Sir Gawain gets hurt. Yet he still back again to fight and again he gets badly hurt.
While King Arthur was away, his nephew Sir Modred began to build an army to overthrow him. He beins first by trying to get the queen to marry him, but that did not work. He even went as far as trying to assassinate the Archbishop. The king and Sir Modred went into an intense battle the resulted with Sir Gawain dying.
The king was preparing to fight again when in his sleep he had a dream. This dream told him that he went into battle tomorrow, he would die and so would a lot of army. With this in mind, both sides met to make a treaty of peace. A misunderstanding with a knight pulling his sword out. This result in both sides declaring war. As predicted, Kind Arthur was fatally wounded.
Sir Launcelot mourned their deaths for a log time. He was un recognizable by the end. The queen wanted nothing to do with him and he was all alone. His heart in the end told him it was his time. He was given his last rights and passed on peacefully.