YES. Your team was sent in to help the ghosts move on as indicated by the contact letter.
IT IS LOST. The newspaper article mentions how the manor was looted and no treasure was found in the mansion.
VACHELLIA CORNIGERA. The fraud painting and other documents reveal Colton had bad intentions. According to the love letter, this plant most mimics those intentions.
BECUNA. This is obviously ghostly code. The locket reveals that she cherishes her orphanage. On the locket, it says 13 ghosts and has a photo of 13 children. Move the letters 13 places in the alphabet to reveal ORPHAN.
If you win the game, the answer is ALL GHOSTS HAVE MOVED ON. If you run out of time, the answer is “NOT EVERY GUEST IS READY TO MOVE ON.” These are the win or lose envelopes.