Dumbledore and the boy

Chapter 1

In Fantastic Beast and The Crimes Of Grindelwald their is some questions about the story and the events happening in it. Though I don't have a question have a statement about the things in the book. Now in the middle I suppose when we see dumbledore we could be surprised. Well when we see his vision there is a chain with something attached to it. We all wonder what it is and when we see the boy and dumbledore using a magic spell we can get a little scared. Well we know dumbledore can't kill Grindelwald. So to think that the vision that dumbledore had with the boy could possibly be Grindelwald and Dumbledore making a promise to not hurt one another that is one thing to think about. This is why Dumbledore can't kill Grindelwald.