C80 A homeless man in a cemetery(4)

"Also," Ding Wei said as he held up the blank book left behind by Lin Hua Wang. "Some of its parts are written with a certain concentration of starch solution, and when smeared with iodine, faint blue words will appear."

Ding Wei found a few marks in the next few pages. He smeared them with iodine and the words appeared.

According to the information provided in the notebook