90's nick halloween show?

there was a (reality) show on nickelodeon during halloween in either the late 90's or very early 2000's and it was a bunch of kids trying to find clues about what happened to this boy that used to go to a camp where they are looking for the clues. and in the end it turns out that he had a twin or something but one of them had fallen down a well at the camp and died. and it was hosted by i believe a british woman. if anyone has any idea what this show was called id really like to know cause i can not remember.