the bat
You have to get the chicken and give it to the farmer that has all the bugs eating his crops.Use the chicken to get the blue light.
The gravestones are in the cemetery to the right of the house. When you have all 4 treasures, and fueled the lantern in the basement, talk to the ghost cat and he will tell you to go to Betsy Blue's gravesite.
Once you have all 4 treasures, get fuel from the kerosene barrel in the basement and see the ghost cat, who will send you to the grave of Betsy Blue in the cemetery.
Once you have all 4 treasures, and fuel the lantern, the ghost cat will tell you where to go, which is back to Betsy Blue's tomb in the graveyard. There should be a hole there that you can enter.
For a mummy costume, you can copy the one from the Haunted House game. The mummies at Nabooti Island are in the Sphinx at Giza. There are three challenges to defeat to recover the Blue Jewel. (see related questions)
Once you have all 4 treasures, and fuel the lantern, the ghost cat will tell you where to go, which is back to Betsy Blue's tomb in the graveyard. There should be a hole there that you can enter.
If you have the chalice already, fuel the lantern with kerosene in the basement. Once you have all 4 treasures, the ghost cat will tell you where to go, which is back to Betsy Blue's tomb in the graveyard. There should be a hole there that you can enter.
In the Haunted Woods. He's the big blue blob thing.
You need all 4 treasures (and fuel for the lantern, in the basement) before the ghost cat will tell you where to take them. There should be a new hole next to the tombstone of Betsy Blue in the graveyard (the crying angel).
blue
There is a large graveyard to the right of the house. When you have recovered all 4 treasures from the house, and fueled the lantern in the basement, the ghost cat will send you back to Betsy Blue's (the crying cherub) and there will be a new hole there.
Patricia Coombs has written: 'Dorrie and the blue witch' 'Dorrie and the haunted house'