Kate Carlson is the mother of Maddy Carlson.
Kate came into the ER with her husband and daughter after her daughter shot her father in order to get him to stop abusing them. She lied to the doctors and said it an accident and downplayed the abuse. Meredith confronted her, wondering why she would let her daughter stay in that situation. After she was told her husband would be okay, Meredith came to her again, apologizing for the way she spoke to her before, but saying she needed to change Maddy's story. That inspired Kate to take Maddy and say goodbye to Mike before leaving him.
She is married to Mike Carlson. He was abusing her and their daughter, so after they were hospitalized, she took Maddy and left.
She has a six year old daughter named Maddy. When Maddy shot her father to stop him from abusing her and her mother, Kate took Maddy and left him while he was in the hospital recovering.