Had a very very interesting situation occur. Was a 4 player game.
Rumor Effect:
"When a monster enters Uptown Streets, place it on this card....."
"Fail: If there as monsters on this card as there are investigators plus one (5 in this case), return it to the box (and all monsters on it to the cup). All investigators are devoured."
There was already one monster on the card. Two investigators were in the streets dealing with the pass parameters. The very next Mythos card called for 2 monsters to be released to the uptown streets. The monster movement also caused 2 monsters in the sky to come down to the location with the investigators. So right there those 4 monsters causes the rumor to fail. My question is do the investigators already there have a chance to deal with any of the monsters? My thinking was the flying monsters move to swoop down onto the investigators therefore having an encounter with them. Does the rumor card in place override this though?
Funny thing is that during the upkeep phase immediately following I was prepared to finish Silas' personal quest. It would have sealed a gate of choice and he would have been devoured, but it would have been the sixth gate sealed. So really the ruling on this either decides whether it was a win or a loss. Even if they would have all been devoured we would have likely gone on to win but it would have felt like losing haha.