The Case of the Green Ghost

"Mary-Kate and Ashley -- I dare you to go into the haunted house!" It was Halloween, and our friend Patty was trying to scare us. Ashley and I didn't believe in ghosts, so we took Patty's dare. But when we went into the haunted house -- we saw a ghost with our very own eyes! There was no time to investigate. We had another mystery on our hands. A case of robbery -- where all the suspects were our friends! But then the clues in our new case led us right back to the haunted house! Were our two mysteries turning into one?