One Through Ten

>At some point of each call state something along the lines of "stump us" and make it sound like stumpus. Gauge each person's reactions and scale them from least to most suspicious.
>Same thing goes for "toxic" or some variation to gauge each caller for potential guilt on poisoning

>This is good plan. Do this.
>Which means whoever does the talking has to be clever, subtle, and good at social interactions.