The Once and Future King Book 3, Chapter 41
Things get darker at court. There is another tournament, and Arthur suddenly begins to assert himself against Lancelot, trying to wound him. Also, Gareth fights against his own brothers, and Lancelot beats each one of the Orkneys--Mordred, Gawaine, Gareth, Gaheris and Agravaine. Agravaine and Mordred later plot against Lancelot, partly for this reason. Meliagrance, a knight who has never felt at home at court and is in love with Guenever, kidnaps her, and Lancelot goes to rescue her.