This is the wife of Brandon Stark. A lord and good friend of the king. The series begins with this family. You realize all the children in this clan do not belong to her. Jon Snow is her husband bastard child. How did he bring this baby home and expect her to suck it up, we never know.
It is clear he is not accepted as an heir. Her son likes to climb and witness the queen sexing up her brother. Jaime Lannister pushes her son from the tower window so no one learns the secret. This is when you see the strength of mothers. She was by his side everyday. Until she realized someone was trying to kill her son. Then she knew there was more to the story.
All this leads to inevitable war after her husband is slain by the King Joffery Lannister. Her oldest son Robb Stark claims to be the king of the north and the war begins. She guides her son in this war. Which he was not ready for and made several big mistakes.
She was more loyal to the welfare of her other children. She only knew how one child was doing during most of the series and that was Robb. The other four were out in the world and she prayed they were alright. She wanted to deal with the Lannister’s to get her daughters back safely. She let Jamie Lannister go which created a problem between her and Robb.
Robb should have paid attention to some of her advice. Such as not marrying the woman he fell in love with. Doing his duty and looking beyond his self to marry one of Walder Frey daughters. This decision marked the end of the Kind of the North and his whole army. His mother tried to warn him. The last scene when everyone was being killed. Catelyn had Walder Frey wife and yelled let her son go or she would kill his wife. Frey immediately said I will get another one.
Her reaction was perfect when they killed Robb. You could feel the pain of her child being killed in front of her. Then she was killed.
She is a very good actress and I appreciated her part in this series.