It turns out that it's not a monster or a child murderer coming at them after all: the "creature" turns out to be Toby and Ken climbing the fence.
The two boys are laughing hysterically after having spied on the kids' Egyptian ceremony. This makes April super mad, and she wants to punch them. A little extreme, but hey, they're mocking her favorite game.
The boys threaten to tell on them, and the kids don't know what to do. They're not supposed to be here at all.
But then Elizabeth pushes forward and begs them not to tell. She says that if they keep the secret, they can play the Egypt Game with them too.
Ken scoffs at this and looks about to leave. At least he says that he won't rat on them.
But Toby stays rooted to the spot. He seems to be considering the game and whether or not he wants to join.
As the kids all head home, April complains about how the game won't be the same now that the boys are joining.