It’s fairly clear what is happening in each of the visible portions of this Perry Bible Fellowship comic, but I really don’t understand the sequence of events between the second and third panels:
I’m pretty sure that the man in the second panel is the same as the one in the background of the third panel, but if was he the one who called 911, how did he manage to escape the “choice”? And what is the EMT on the sidewalk trying to communicate with her hands?
Comics I Don't Understand 
The man in grey in the second panel is in the ambulance which was called by the woman with ginger hair who has had second thoughts about her cult membership and dumped her robe in the bin.
The EMT on the sidewalk is indicating to the distant couple that “there is nothing to see here, everything is under control”.
I imagine that the cartoon is just a dressed-up dramatic illustration of the facts about liking to eat mushrooms that you pick yourself in the woods: pick the wrong ones and you die. So to be able to join the mycology club (and be able to advise members of the general public) you have to be able to demonstrate an ability to distinguish edible from poisonous mushrooms.
Perhaps, though probably unlikely, in this particular case the ginger-haired woman realised that the perp deliberately offered the noob two dangerous mushrooms, intending to kill him, and the noob didn’t realise that either option would lead to death.
The man was offered a choice of mushrooms to join their order. One was edible and the other poisonous. He choose the wrong one and died. The joke at the end is that it wasn’t some mystical order but just a mycology club at the local library.
I don’t see a third panel, am I missing something?
It seems to me that hooded guys are offering the choice to gray guy. Second panel, gray guy is in the ambulance and two of the hooded guys are being arrested.
And as Kevin points out, it’s not a horrifying secret society at all.
Chak, the top is divided in two. That’s obscured because the speech bubble from 1 spills over.
I agree with Ian.
@ George (6) – I was very grateful for Ian’s analysis @1, which seems to solve the whole story, but it revealed one detail that I never noticed before: what happened to the fourth member? (The simple answer being “out of the frame to the right”.)
Mitch4,
Ah, got it! Thanks
The sign for the meeting looks hastily done and put up. Like it was a pretense to lure people to the cult members/aliens to get them to eat a mushroom. The guy who ate it is in the ambulance. The two who offered it are arrested. Not sure about the others. Maybe the hood without eyes were aliens who could disappear?