Marlena talked her way out of it YET AGAIN & idiot John brought it.......
Marlena said something to the fact that she heard someone & was scared it was the stalker! That is why she had the knife.
I don't know why John thinks his precious "Doc" can't possibly be the stalker. If it were ANYONE else (ok, probably not his little "Princess" Bell ) John would be all over that person saying they are the killer!