Proluge-In another world

Katniss, Peeta, and Gale tell Lockwood and co about how they got here, but when their story is cut short by a stranger in a cloak telling them that their world is going to collapse they seek help from a certain alien ( who will stay in prison)from Hully . Will they stop the collapse of their world? Who is the stranger in the cloak? And no Travel through worlds is in no way connected to this. I own nothing but the plot and Gordan.