Question

Why did the ghost in the shady plot appear in bits and pieces

Answer 1

the ghost wanted to fear out the writer also was indeed happy by making other people scare.

Answer 2

Since Helen was ghost  . She used to  help those who did not have any plot about ghost fiction when they sat to write such stories and people used to bother the ghost by using Ouija boad so she was in mood of strike so she appeared in bits of pieces  before Hallock to inform him that she and her companion would not help him creactin any plot when he would sit down on chair to write ghost stories