You’ve been unexpectedly imprisoned in a hellish overseas grotto. Besides your captors, the only person present is another prisoner, one cell over. You cannot see them, but if you whisper, you can communicate without being overheard.

As the days wear on, together you begin to develop a plan for escape.

You are nervous, though: much depends on your ability to trust your fellow prisoner, and your furtive whispered conversations have done little to offer you any evidence this is wise.

You decide to bring things to a head before continuing, and so, using a stray piece of coal and a page ripped from the only book in your cell, you fashion a crude note.

“No, No, No,” you write.

After lights-out you manage to toss the note into your coconspirator’s cell.

The next evening the crumpled note returns.

“Yes, No,” has been added.

Escape is in your grasp.