Arthur and Lancelot are watching Gareth practice with his bow. Gareth became a knight by escaping from Orkney and becoming a serving boy in the kitchens at Camelot. Lancelot had noticed him, trained and then knighted him—all before his brothers knew who he was. While they watch, Gareth receives a letter; he reads it over and the color drains from his face. He tells Arthur and Lancelot that his brothers, Agravaine, Mordred and Gawaine have killed his mother because they found her in bed with Pellinore's son Sir Lamorak and then stabbed Sir Lamorak in the back.
The cruel and perverse killing of Morgause by her own sons illustrates the peculiar relationship she maintained with her children. Her neglect made them devoted to her and intensely jealous of her attention. Finding her devoting that attention elsewhere and in a dishonorable way proves too much for them. The stabbing of Lamorak in the back indicates a willingness to "play dirty" that is foreboding.