Day 90 - An Ancient Repair

My aunt has an old crocheted granny square blanket. Well she has several. I believe that they were made by my great-grandmother on my mother's side. But the one I am talking about is damaged. I need to figure out how to fix it. I have no idea where to start as I have never done this before.I think it will just take a little time and several hooks. I may also need some replacement yarn. I am not exactly sure yet but I will have to look into it.