What happened in the middle of night to the tent and its inmates on rainy day?

The tent blew down in the rain, trapping its inhabitants underneath, where they all got tangled up with each other. 

“Bally tent’s blown down, I think,” he says.

Then you both raise up your voices and shout for “Bill!” and the ground beneath you heaves and rocks, and the muffled voice that you heard before replies from out the ruin:

“Get off my head, can’t you?”