The second appearance of Amy Aquino in the series. First appeared in Mr. Monk and the Red Herring (2005) as the woman who interviewed with Adrian as a potential new nurse for him.
Ammonia and bleach actually make chloramine gas. Bleach and acid (like vinegar or hydrochloric acid) make chlorine gas. While both are toxic, chlorine is deadlier. (Pool cleaner chlorine and the uric acid in urine make the pungent pool smell of trichloramine and cyanogen chloride; both are toxic).
In reference to the members of a therapy group's being reduced through death, a surviving member of the group says, "... and then there were three." This is a reference to the poem in Agatha Christie's Book, "And Then There Were None."