Who walked into Janet's house?

I don't know if this has been discussed or not, but shortly before Janet burned her old house down, someone came in there and walked around while she hid (current in madddie's body). I just assumed it was Mr.Martin but what do y'all think?

Also, unrelated but I just need to know Yuri's background story, like when are we gonna get to know what happened lmaooo 😭