Scarlette Skelly is a pupil at the newly created school for ghost kids where the Head Master, GH. Öst, is determined to educate the pupils on the rights and wrongs of being a ghost. Scarlette's family are all skeletons so other pupils have nicknamed her 'Bones', which she kinda likes but pretends not to.

Head Master Öst gives all his students little tests, to see how honest and dependable they are. So, he has given Scarlette a key and told her it is for a cupboard in the school that must NEVER be opened. The other kids are fascinated by what might be in the cupboard, so they constantly ask her to secretly open the cupboard. But she knows this is a test that Head Master Öst has set her, so she resists. Scarlette and the other kids find clues as to what might be inside the cupboard, but she never weakens in her resolve to pass Head Master Öst's test.

However, one of the clues suggest that what might be in the cupboard could help everyone.

What will Scarlette do? Keep her promise? Or take a chance for the common good?