Who is the traitor Yuan Ge is looking for?

In the TV series Romance of the Great Song Dynasty, the traitor Yuan Ge was looking for was Lu Guannian, the head of the Privy Council. It was he who handed over the marching route of the army to the enemy, resulting in only the Yuan brothers surviving, and he was also suspected as a traitor by the court. From then on, he began to look for traitors.