[Carth]

My curiosity is how and where it was administered, and in what 'form' the substance used was.

They were found 'unconscious on a park bench' in the open air.

A policeman who came to their aid also became infected. Did the policeman become infected because he attempted mouth to mouth resuscitation on one of the victims?

If not, was the substance on their skin, their clothes, the bench?

Presumably it has to be either liquid or solid, as a gas would have dissipated long before help arrived?

If so, what would all 3 people touch? A carrier bag, sandwich bag, bottled drink, cigarettes?

I'm sure the answers will be revealed eventually, but I do like a good 'how did they do that' discussion.