"Okay, Inez," you say. "I'm sorry I snapped at you."
Her head pivots like it's on casters. "Try that again with a little less exasperation, please."
"I'm sorry."
She studies your face for a long time. Then she raises one eyebrow and asks tartly, "May I continue, then?"
"Please do."
"Just like a maze with no branches isn't really a maze, neither is one where all of the branches end up taking you to the goal."
"All the branches but one have to lead to dead ends instead."
"Right," Inez says. "The dead ends define the puzzle almost more than the solution does."
"Well, in mazes, at least."
"Not just mazes. All puzzles. All puzzles are defined by their dead ends."
You pause to think about that one. "That's not true," you counter. "Where are the dead ends in a crossword puzzle? A jigsaw puzzle?"
"Or a sudoku."
"Right."
Inez's face slowly lifts into a grin and you realize the trap you just walked into. Keeping her eyes locked with yours, she slowly leans forward and reaches into the backpack sitting at her feet. She fishes out another one of her envelopes.
You have to fight to keep from rolling your eyes.
"Oh, don't worry," she says. "This one's for me."
"Really?"
She nods earnestly and then pulls a sheet of paper out of the envelope. She unfolds it and places it on the desk in front of her, revealing a sudoku grid:
"There are dead ends all over this grid," Inez tells you. "In fact, there are 1,620 of them."
"Show me."
"Well, here," Inez says. She reaches into her backpack again, coming up with a pen, and then makes a big show of smoothing the sheet of paper flat on her desk. "What's the point of a sudoku? How do you know when you've solved it?"
You shrug. "When all the boxes are filled in."
"Right," Inez says. Then she hunches down over the paper and you can hear her pen scratching. A quick glance over your shoulder reveals that Randy has fallen asleep.
"Done," Inez says, putting down her pen with satisfaction. "That was so easy. I don't know what the big deal is." She hands you the paper.
"But you can't do that."
"You said all I had to do was fill in all the boxes."
"Well, yeah – but you can't have the same letter appear more than once in a column or row."
"Or section," Inez adds. She gestures towards the paper. "But obviously I can, 'cause I just did."
"Well, you can fill in the grid with happy faces if you like, but then it's not a sudoku."
"Right," Inez says. "It's not a sudoku – it's not a puzzle – because there are no dead ends."
You shake your head. "You've lost me again."
"Here – let me show you." She glances down at her completed grid and then says, "Oh." Then, without missing a beat, she fishes a second sheet of paper out of the envelope. "This one's for you."
"Of course it is."
She scoots her chair/desk combination up next to yours. "Here." She points to the upper left-hand corner of the grid. "What can you tell me about this square?"
"Okay, let's see. The row already has an A, H, C, and F, so it can't be any of them. And the column has an I, D, G, and another A. There's a B in the same section."
"Right," Inez says. "The rules won't allow me to put any of those letters in that upper left-hand square. In other words, the rules have made all of those options dead ends."
"I see where you're going now."
She smiles. "That's one of the main functions of the rules in any game: to create the dead ends. It's what I love about sudoku: you fill in each square not by figuring out what letter must go there so much as what other letters can't go there. It's a process of elimination." She glances back down at the paper. "So: with all of the letters we've eliminated, what do we have left?"
"Let's see. A, B, C . . . . E. The only one left is E."
"That's a good start," Inez says, and she vanishes. The pen she'd been holding clatters into her now-empty seat.
"Of course," you say to the all but empty room.
You can solve the sudoku and find the solution on the Solution Page. Or you can