When I was in my teens, Agathe Christie’s Curtain, Poirot’s final case, was published. A friend read it before I did, and told me there was no way I’d figure out the ending. We had had discussions before about mysteries. I had been a big mystery fan as long as I could remember—not surprising, since my mother had read Heinlein and Christie novels aloud to me as a baby and toddler.

We ended up in a bet about whether I would figure it out. He bought a second copy of the paperback and rigged it up with a seal covering the last fifty or so pages. I would read it to that point, stop, and then not read further until I had told him my guess.

I did it. He was carefully examining his seal when I told him who the killers were and what had happened. He stared at me, open mouthed. “You swore you wouldn’t read another copy or ask anyone how it ended!”

I insisted that I had done neither, and asked him if I was correct.

He threw the book at me and stomped out.

I tore the seal off and finished the book. I had gotten it right, not quite down to every detail, but I had definitely solved it.

For at least a year afterward he would occasionally accuse me of cheating. Other times he would bring it up, say he believed me that I hadn’t cheated, but still couldn’t understand how I did it. He would tease me that I should become a cop instead of pursuing my writing dreams.

I want to be clear here that I did not cheat. I didn’t peek. I didn’t overhear anyone talking about it. I didn’t find another copy. I didn’t ask anyone about it in any way.

But, it could be argued that I had a some possibly unfair advantages:

1. I literally had been listening to and reading mystery stories for longer than I could remember.

2. I had been intentionally studying the art of crafting mystery stories: reading countless articles in magazines like The Writer and Writer’s Digest, getting books on writing fiction in general and mystery in particular through interlibrary loan, writing mystery stories of my own. I was exceptionally well-versed in the tricks of the trade.

3. I was familiar with Christie’s writing in particular.

Those probably weren’t unfair, really, however:

4. I knew that Agathe Christie had written this book 30 years earlier intending it to be the fitting end to Poirot and Hastings’s careers. She’d originally stuck it in a vault to be published after her death. She agreed to the publication in ’75 because she knew she was dying and would never write again. That narrowed the possibilities of how the story would end.

5. I knew that the ending was something which this friend, who was no dummy, had thought was completely unforeseeable. Again, that made it easier to pick from the possibilities that occured to me as I contemplated the clues. Another way to look at it: that prompted me to at least contemplate possibilities which might otherwise seem too outlandish to consider.

This friend once asked me how could I enjoy mysteries at all if I often figured them out before the end. He is hardly the only person to ask that.

For me, part of the fun of a good mystery is finding the puzzle pieces in the storyline and admiring how well they are constructed, or how good a job the author does of putting them in plain sight while not making them obvious.

Sometimes I am completely blindsided, and if that happens without the author cheating, that is just as much fun as figuring it out before the reveal.

Bad mysteries aren’t bad simply because they are predictable. They’re bad when they are too predictable. When the author (or author and director, in the case of a movie or show) clumsily gives things away or relies on cliches, there is no delight in the reveal. If the author cheats by simply withholding information, or otherwise pulling something bizarre and shocking out of nowhere, that also spoils the fun.

And, as in all stories, if the author makes us care about the characters, even if the puzzle isn’t terribly difficult, we can still enjoy the battle of wits between the detective and the same puzzle.