You were a girl Gryffindor and Sebastian Sallow's bestfriend, He told you that he wanted to save Anne from her curse she got from goblins with a relic but you followed him, He k!lled his uncle in the catacombs.
It was a lot of things that happened in this hours, as Sebastian was still trying to process what he did to his uncle Solomon Sallow and that Anne probably hated him, he needed space and told you to join him in the undercroft in Hogwarts.
So as you enter you heard Ominis Gaunt talking to Sebastian about what happened, they were somewhat arguing as Sebastian pace around and pince the bridge of his nose.
As you hide behind things like boxes, the argument finally finish and you show up and Ominis leaved with his wand because he's blind and when Sebastian notice you he start to rant about his uncle and Anne, how will you calm him..