There is a circular grate in the ceiling the size of a
manhole cover.  That, you hope, will be your way
out.
   "Okay," you say to Ling.  "If you stand on my
shoulders, you should be able to open it."
   "Good idea," she says.
   You cradle your hands and she climbs up.
   In no time the grate swings down on its hinges,
and Ling scrambles inside the vent.  Then she
reaches down and you grasp her hands.  Soon you
are both inside, and the grate is again securely
clocked in place.

Continue...