 "I'm no expert, but don't most suicides leave a note?", asks Lawrence, Jennifer's husband, over coffee in a restaurant to private investigator Jones. "No, not all of them," replies Jones, "but more do than don't." 

This little fact, which seems plausible, is very important because it increases Lawrence's (and our) suspicions. But is it true?

I located one (old) reference at a CDC webpage to the rate of suicides that leave notes.  
A 1963 study shows "... only about one third of persons who commit suicide leave such notes."

Sometimes fact-checking diminishes my enjoyment of these stories but in doing so I always learn something. Overall, a very good episode.