The Phantom airman

This story is difficult understanding for me because it mixed the story of past and the story of present in the novel, although the story is interesting.
The four kids investigates various thing related to the phantom airman.They are brave and curious.
There are a lot of the story of past in the story. Their experience of the past are taken hints to solve for this story's mystery. They got many hints of the past and solves mystery at the present.
I think the Glen of the phantom airman was complaining to the present people about traitor is too bad.
I regretted having my low knowledge of English about grammar, word and so on. I don't understand easily.I hope to become understandable a man.