What are Olesen's diaries?

Olesen’s diaries, including a secret diary hidden in a book about World War I, provide major clues to his death. The diaries reveal, especially in the final months and days of Olesen’s life, frequent encounters with people from his past. He describes them as ghosts “crowding him” into his grave. The diaries reveal Olesen’s growing fears about dying, reference his “greatest sin”, and panic about dealing with Deerfoot in the particular. The people referenced in the diary are referenced by code letters – “D” for “Deerfoot, “O” for OSS for Darrell, and so on. The diaries help K2 and Patricia to understand more about Olesen’s frame of mind and motives for his actions just before his death.