September, 1992. Hogwarts. The incoming class of children have been Sorted, and all the students and staff are settling in to partake of the delicious feast. First-years are getting to know their new housemates; old friends are sharing news of the summer. At the high table where the faculty dine, there is (as there so often is) a new colleague to meet.

Minerva has gotten a seat next to said new colleague, by the power of seniority and gravitas. Filius is on his other side, by the power of being too short to hear the conversation if he isn't. Pomona is on Filius' other side and enthusiastically leaning around him asking, "So you're from across the pond, then?"

"Yes, ma'am. Department of Magical Law Enforcement, California division. And a diehard Los Angeles Lizardfolk fan as well, dunno if you do much Quidditch around here."

"We do indeed. I'm afraid I don't follow the American leagues, but there's a thriving British Isles league, and of course you can watch the next generation of players right here at Hogwarts."

"I'll plan to do that! That's great. The Houses sort of split kids into teams already, don't they? And that Sorting was something else. I tell you, if we had a Hat in the department that could look inside people's heads, maybe my job would be a whole lot easier. But what do I know. Say, what's this food?"

"Treacle tart!" chirps Flitwick, "And if you haven't had it before, I highly recommend it."

"Thank you." Columbo chews the treacle tart thoughtfully.

"Where's it all come from? So many different dishes, it must take a whole lot of work."

"We have the largest staff of house elves of anywhere in Britain, and they do an excellent job."

"Oh, I see. Is that a fact? I've never met a house elf before—we don't really see a lot of them in L.A. Same as with ghosts, in a way. I mean, occasionally you'll get a haunted hotel room, we had a ghost stampede at La Brea a few years back, that kind of thing, but nothing like this." He sweeps his arm in the general direction of the ghosts throughout the hall.

"You can really tell you're in a place with a long history. I was just reading about the Hogwarts ghosts on the train. It must be amazing to live here all the time, huh?"

"It really is." It's hard to remember that, sometimes, but never at the start of the year. Not when she gets to lead the first-years into the Great Hall and watch the same awe spread across every face, the purebloods who grew up in mansions and the muggleborns who learned about magic a few weeks or months ago.

Flitwick smiles too. It's a great place and he's glad the American appreciates it properly. "I quite enjoy it. Is this your first teaching post, then, or have you taught before?"

"Me? Oh no, not really. Coupla lectures here and there, never full time. No, this is a brand-new opportunity. Turns out Professor Dumbledore pulled some strings with my boss's boss, and here I am—teaching in a thousand year old castle! Would you believe it? I wonder how they do that enchantment with the ceiling. Very atmospheric. I just bet it says something about that in my book. So what do you teach, sir?"

"I teach Charms," says Flitwick, "which makes me just the man to ask about the ceiling!" And he's grabbing the portkey to infodump town for as long as Columbo cares to indulge him. With some help from Pomona, as it transpires that the Great Hall ceiling is composed partially of living, magically camouflaged skyvines.

Columbo has inexhaustible interest in this frankly breathtaking feat of magical architecture! And Pamona and Filius make excellent dinner companions; Filius is sharp as shears, and Pomona has a completely unpretentious way of knowing seemingly everything there is to know about Herbology. It's going to be an interesting year, he thinks.

Eventually the bottoms of serving-dishes and the tops of plates become visible, and the students are led up to their dorms, and the faculty retire to the apartments near their respective classrooms. 

And in the morning, there are classes. Starting with, thanks to the inscrutable whims of the schedule, the second year Gryffindors.

This one is looking at him with an expression Professor Columbo may find familiar, if he's ever done his job in a room with a mirror.

Oh, that scar. Through practiced stoicism, Columbo manages not to let on. Kid probably gets enough attention as it is. But he files away that scar, and that look, and he glances around the whole classroom of second-years, and finds the beginning.

"G'morning class. I'm Professor Columbo, and this is Defense Against the Dark Arts.

"Defense is, famously, a very big subject: it's not about a particular kind of magic, like Transfiguration is about changing substance, or Magical Creatures is about animals, or Potions is about putting natural magic in bottles. Oh sure, you've got to know a little bit of all of these, that's the foundation of Defense—and I will be talking with you and your other professors about what you can already do, so we can build on that— but Defense isn't any one type of magic.

Defense is a way of thinking. Using your brain, and what you know, and what you've practiced, to deal with magic that can hurt. Dark Arts: magic that can hurt. In this class, you're going to learn how to do that. Or I oughta say you're going to bring your ability to another level; I know I'm still learning more about Defense, all these years later. You've got to know your stuff, first of all. We'll be learning a bit about curses, and poisons, and Dark creatures. And then—I'm a very practical person— you've got to be able to recognize what you're dealing with. Outside of a classroom, no one's going to say 'Hey, I'm about to turn your legs into jelly', and no one's going to label the hinkypunks from the will-o-wisps. You've got to be able to recognize what you know in an ambiguous situation."

He pauses thoughtfully. "Let me give you an example. Suppose you've just seen someone—your grandmother, maybe, a very nice lady, you love her to pieces—curse your neighbor's tree, and the next day the tree dies. It sure looked like her, in her usual purple shawl, but you're pretty sure your grandmother would never do that kind of thing, or never willingly. It's a very strange situation. An ambiguous situation. Now I want to hear your ideas. What Dark magic do you know about that could explain this? Maybe it's Dark magic, maybe it's a misunderstanding or a deception or coersion, anything that could make it look to you like your grandmother just decided one day to curse a tree, when really that's not true, or not the whole story. What do you think?"

The girl who looks like she got her initial rations of hair and teeth and immediately got back in line for seconds gleefully puts her hand up. Everyone else seems to consider this a sufficient collective response.

"Yes, ma'am!"

"It could be someone who took Polyjuice potion to look like my grandmother, or just disguised themselves as her with clothes and makeup. Or Transfigured themselves, but that would be dangerous. Or she was threatened into doing it. Or she thought she saw a dangerous creature hiding in the tree."

"Terrific thinking, Miss—?"

"Granger. Hermione Granger. Thank you, Professor."

"Miss Granger is showing us how to juggle different theories at once:

What if it was somebody else? Maybe it was Polyjuice potion, great answer: a sophisticated potion that makes you look like somebody else for about an hour. Self-transfiguration, very dangerous like you said, I don't recommend it, desperate people sometimes do it, very possible also. I especially like that Miss Granger included disguises: magic folk sometimes forget about disguises, which you can do without magic and which leave no magical trace behind.

Or What if my grandmother was forced? Threats are one way to do that, yes, and perhaps you've heard of Dark magic that can do that, too.

What if we assumed the wrong motive? Very important! In day to day life, answers seem obvious. You observe, you conclude, and there's no gap between what you're seeing and what you're concluding. What if my grandmother wasn't trying to damage the tree, but swatting a dangerous creature. It's a very important defensive skill, to separate what you observe from what you assume. You need it in all kinds of Defense work, whether you're a curse-breaker, a detective, or a duelist. We'll practice that also.

Here, we're seeing how to juggle several different ideas that may not all fit together, without getting stuck on any particular one. The point is to question as much as possible, to make as many as we can think of. Anyone else think of more we can add? Other motives? Any magical forms of coercion? What about magic that could be targeting me in this situation?"

Granger puts her hand up again!

And so does a round-faced nervous-looking boy, very tentatively.