I really liked this story. I like that the setting is also given in sips and bites, just like the title. By the end you know everything you need to know, but it's all done without big infodumps. Half the fun is just trying to figure out the setting.
I also really like that, other than the apparently invincible stranger, there was no speculative element. I could totally see people actually doing this, and that makes it more real. The identity of the stranger is kept entirely in the dark, whether he is just a man with seemingly impossible poison tolerance, or if he was there to dispose of them, or to test their resolve.
I like the "third time is a charm" aspect of his blackouts, once in the light, once in the darkness, third time as yet undetermined. Sort of makes me think of the later story "The Greatest Adventure".
Ben Phillips did the reading very well, I like the accent he used for it.
Nothing to complain about this one, great show!