Ben trailed behind the military escort a trifle grudgingly. Arguably, they were the best equipped to handle whatever they might encounter, but that belief didn't reassure the part of him that wanted to rush to Harry's assistance, not at all. He imagined that same feeling was only worse for John.

The squad went through the trapdoor first, casting cushioning charms as they went, then called up that it was a very long fall but there was a soft landing … onto a bed of Devil's Snare.

Getting past the Devil's Snare was trivially easy - with seven of them casting incendiary spells at it, it disappeared in about that many seconds.

Now, the party crept along a passageway that had to be at least somewhat magical in nature judging by its length. Ben couldn't imagine anyone would ever have carved a mile-long tunnel beneath the castle otherwise.

A hiss from both Sentinels in the party made them stop.

"Buzzing," John reported. "Like thousands of bees."

"Larger wings than that," Alpha Sentinel Mallory said. "Very small birds, perhaps."

Ben cast a protective shield around Wendell Granger, and only remembered it was rude to do so when Gran Ran hit him with a stinging hex. He winced and turned to the other man.

"Sorry, I should've asked first," he said. "Just a bit of a shield. The men will see to the Alphas - I just wanted to be sure you weren't forgotten."

"Thanks," Granger replied. "No offense taken."

"Right," Alpha Mallory said. "Forward, with caution."

A bit further along, the passage widened into a brilliantly lit chamber with a ceiling vaulting high over their heads. The ceiling arch was full of small, jewel-bright birds, fluttering and tumbling around. A heavy wooden door dominated the wall on the far side of the chamber.

Only - those weren't birds flitting about, Ben saw in the same moment his Sentinel reported the fact. They were, in fact,

"Keys," John said. "Winged keys."

"And broomsticks standing in the corner," Alpha Mallory added. He frowned. "You lot actually fly on broomsticks?"

"Sometimes," Ben answered. "And there's a flying sport called Quidditch."

"Right," Alpha Holmes said. "Presumably, we're supposed to fly up there, find the right key, and use it to open the door."

"Bollocks to that."

Ben just stepped aside to let his Gran through.

"As impressive as this is," she said, drawing her wand - the fourth, or perhaps fifth, she'd had in her life; curse-breaking could be hard on a wand - and casting a spell that covered the entire room in a soft silvery light. "It is still simply layers upon layers of charms. Charms can be broken."

"Wouldn't they have thought of that?" Wendell Granger asked. "I mean, I'm new to magic, but it just makes sense to prevent things like that."

Gran looked over her shoulder at him, grinning briefly. "You'll find that wizards rarely make sense. In this case, however, you are correct. Whoever charmed the keys layered in strengthening charms as well, so that it'll be an undertaking to remove them. I'm not saying I can't do that, mind - just it will take time."

"Do you think the correct key is still here?" Alpha Holmes asked. "Wouldn't whoever got past this before us take it with them?"

"That would be the intelligent thing to do," Gran said. She cast another spell Ben didn't recognize. "And someone did, in fact, take away the key, if my scan for compatibility is correct."

"So we're stuck," Alpha Mallory said. "At least until you break the charms on the room."

While the others discussed their options, Ben crossed the room to examine the door itself and especially the keyhole and lock assembly.

It appeared to be an old-fashioned lock, rather than a modern one.

Ben smiled. Good. He wouldn't even need his lockpicks for this.

He pulled a pen from a pocket and transfigured it into a key that might fit the lock. He gave it a try, only to find the key was a bit too small.

He tried the transfigured key again and again, making small adjustments each time. Finally, he had something that sounded and felt like it fit properly. Now to get past whatever magical protections were on the lock itself.

"Gran?" he called, straightening from where he'd squatted to work on the transfiguration. "Can you mimic the caster's magic? I've made a key that should otherwise work."

"Hmmm…" Gran's wand danced in elaborate patterns Ben didn't even try to identify for several minutes before she smiled.

"I can't mimic it, but-"

She turned to look at the others. "You'll want to be behind shields for this."

Ben backed off and joined John and the soldiers in weaving layers of protective shields. Thanks to years of her stories, he knew better than to put a shield around Gran - she couldn't effectively cast the spells she needed through a shield. That was just one reason curse-breakers tended to have relatively short careers - and lives.

Before he could do more than erect the shield, Gran jabbed her wand toward the key. It turned … and then exploded in a soundless flash of magic.

Then he was shifting his shield as the charmed keys fell.

When the last tinny echo of metal falling on stone had faded, Ben released his shield, then hurried to Gran's side.

The force of the magical explosion had sent her flying into the shield Ben and the others were maintaining, and she hadn't moved since.

A quick scan, both magical and mundane, told him she was simply unconscious, so he shot a Reviving Spell at her. A minute later, he was helping her to her feet.

She turned and looked at the gaping hole where the door had been and the dimly-lit room beyond. "Well, then. Are we continuing?"

The question was answered by Wendell Granger's call of, "Hermione!"

He dashed forward, outpacing even the Sentinels in the room.

Then they were in the room beyond, and Ben saw Wendell kneeling next to a child with bushy brown hair.

"Are you all right?" Wendell asked.

The child - presumably Hermione - looked up from where she sat on the floor, leaning against a wall. "I think my leg's broken, but that's it."

Wendell's face darkened. "Where's your Sentinel?"

"He went ahead. He had to, Dad," Hermione added earnestly. "Otherwise, Professor Quirrell would get … whatever it is."

"What happened to your leg?" Wendell asked.

"We had to play our way across." She pointed further into the room, and now Ben saw the remains of a giant chessboard. "We took the places of a bishop and a castle, and at the end, I had to sacrifice myself to win."

"Hermione, is it?" Ben knelt at her other side. "I'm Guide Detective Sergeant Ben Jones - Harry's uncle. I'm also a wizard. Will you let me heal your injury?"

"Can you?" Hermione asked. "I mean, I'm sure magic can do lots of things we haven't learned yet, but-"

Ben held up a hand. "No, I'm not a healer, but I can mend a simple broken bone."

"Oh. Okay, then."

Ben pointed his wand at her leg and said, "Tibium emendo."

Then he offered his free hand to Hermione, and Wendell offered her a hand as well.

"Don't," Ben said. "Harry doesn't know you yet. He should recognize the familial relationship by scent, but if he's in a territorial drive - and I think he might be - we shouldn't risk it."

Wendell nodded tightly and rose, taking a step back in the process. Hermione took Ben's hand and he pulled her to her feet, steadying her while she tested her leg.

"Thanks." She smiled up at him, then looked around, wide-eyed, at the other people in the room.

"Introductions later," Ben told her. "Except Sentinel Detective Chief Inspector John Barnaby, Harry's dad."

Hermione murmured a, "Pleasure," and then took a few steps to the chessboard, frowning. "It's reset itself. We'll have to play across again."

"Then it's a good thing my FIDE rating is 2596," Alpha Holmes said calmly enough. "What do we do?"

Hermione stared at him for a moment before taking a breath. "We take the places of the black pieces and we have to win the game to get across. But - sir - the pieces, they're magical, and they actually fight when they're taken. Or they're taking you."

The Alpha smiled at her. "Thank you for your concern, but I believe we'll be fine. Right, then - Ms. Jones, if you'll kindly be the queen? Gareth and Barnaby, the bishops. Jones and Granger, the castles."

Ben tagged in, the black bishop moving away. Around him, the other people Alpha Holmes had named did the same.

"What about me, sir?"

Ben turned on his square to see Hermione looking gravely up at the Alpha, just as Wendell said, "No, Hermione!"

Alpha Holmes speared Granger with a look. "Are you attempting to prevent a Guide from joining her Sentinel, Guide Granger?"

Granger flushed, and his embarrassment shrouded the chamber. "No, Alpha. Sorry, Hermione. I was just being a father before I was a Guide."

Hermione just smiled, quickly, at her father, before turning back to Alpha Holmes with a determined expression.

"What would you prefer, young Guide? A knight or a pawn?"

"A knight, sir."

"Right, there you go - queen's knight." Holmes gestured her forward, then addressed the soldiers. "I'm taking the king's position and will be in row eight. The far side of the board is row one. To my far left is column H, and to my far right is column A. Got it? Excellent. If you'll take alternating pawns, beginning with A7, then A5, and so on. Thank you."

Finally, the Alpha took his place and bowed, oddly regal, toward the white pieces arrayed opposite them. "Let the game begin."

Ben watched a white pawn move to … he counted quickly in his head … F4.

"Surely not?" Alpha Holmes sounded completely baffled. "Surely … E6."

Gran had to nudge the soldier standing on E5 to move forward a square, but he did.

A white pawn moved forward to G4.

Alpha Holmes gave a dismissive snort. "Well, if you're going to be that stupid, you deserve this. Queen to H4, please." Gran moved diagonally across the board, and Holmes said, "Fool's mate."

The white king doffed his crown and bowed. Then the white pieces parted to form an aisle.

Ben started forward, following the soldiers, only to smile when he heard Hermione's irritated voice.

"It was much more difficult when Harry and I played through."

"Remember, lass," Gran said. "Magic is based on intent. When you and Harry played through, you were intent on getting through to find whatever's on the other side."

"To keep it safe!" Hermione said.

"You suggest an ability to discern shades of meaning that I don't think is possible," Gran said. "We - specifically, Alpha Holmes - wanted only to protect the castle and the students within, and his commission from the Queen speaks to that purpose. The game was merely a means to that end."

"Hm."

Gran chuckled. "We'll speak later, lass. First, we have to find young Harry."

"The next room, there's a troll," Hermione said. "Harry thought it was dead, but it could just be heavily stunned. Then beyond that, there's a potion logic puzzle. Harry managed to get me the clues through our bond, and I think-" her voice quavered suddenly. "I think maybe it didn't work right, because it was right after that that I lost him - lost my sense of him."

"Then I suggest we hurry," Alpha Mallory said.