"What do you think he will do?" Bob asked Alison. Bob had a feeling that these secrets are important, but as long as they kept them secrets, Mr. X wouldn't let them go. Alive, at least.
Hearing Kas's words, he replied. "I don't have anything to hide. What was written in the letter, my police department knows about it. My family knows about it. What about you? Are you sure you're not hiding anything?" he said, sensing his facade. He was an officer of the law, and almost a detective too. It was second nature to him to sense the truth about people.
"I think we shouldn't hide our secrets. That's what Mr. X expects us to do." he said to the three of them. If Mr. X wanted them to keep their secrets, he wouldn't have sent private letters. He would have told them out aloud.