Bob sighed.

Merlin walked into the woods in comically fast motion and vanished. Then time passed. The sun streaked by hundreds and then thousands of times, the shadows of the island bowing and twisting, the trees rising, growing, growing old, and dying. At the bottom of the screen, words appeared that read, A LOT OF TIME PASSES.

"Thank you for dumbing that down for me," I said.

"De nada."

Then the camera slowed. Again, Merlin appeared. Again, oceans of power rose up and settled into the island. Then Merlin vanished, and more years passed. Maybe a minute later, he appeared again-looking exactly the same, I might add-and repeated the cycle.

"Hold on," I said. "He did it again? Twice?"

"Ah," Bob said, as a fourth cycle began on the screen. "Sort of. See, Harry, this is one of those things that you're going to have trouble grabbing onto."

"Go slow and try me."

"Merlin didn't build the prison five times," Bob said. "He built it once. In five different times. All at the same time."

I felt my brows knit. "Uh. He was in the same place, doing the same thing, in five different times at once?"

"Exactly."

"That does not make any sense," I said.

"Look, a mortal jail is built in three dimensions, right? Merlin built this one in four, and probably in several more, though you can't really tell whether or not he built it in a given dimension until you go there and measure it, and the act of measuring it will change it, but the point is: This is really advanced stuff."

I sighed. "Yeah. I'm getting that. But what's wrong?"

The shot zoomed out, rising up to give a top-down view of the island, which became a blurry shape. A familiar five-pointed star blazed itself across the surface of the lake, its lines so long that the pentagon shape at its center enfolded the island entirely. Within the pentagon, a second pentacle formed, like the first one drawn in the manner to preserve and protect. The camera tightened in, and I saw that the second pentagon enfolded the entire hilltop where the cottage and ruined tower lay. The camera tightened more, and I saw more pentacles drawn, this time not flat but at dozens of intersecting angles, their centers encircling the dozen tunnels full of evil beings beneath the island.

"These," Bob said, "represent the original enchantments on the island. This is vastly simplified, of course, but the basic star-and-circle architecture is the same as the work you do, Harry."

Then the design blurred and increased, growing denser and more delicate and more brilliant in power, until something twinged in my brain and I had to look away from the diagram.

"Yeah, sorry about that, boss. This is meant to represent the entanglement of the spells being delivered at different times."

"No wonder it was so complicated," I muttered.

"And it's even worse than this," Bob said. "I'm filtering it down for you. And here's the problem."

I forced myself to look back at the projection, and saw those millions upon millions of spells resonating with one another, spreading and interlocking into an impenetrable barrier. It was, I thought, somehow like watching crystals grow. The spells powering the actual construction of it hadn't been, alone, too much stronger than some of the work I had done-but when they'd been interconnected with their counterparts across time, they'd fed upon one another, created a perfect resonance of energy that had become something infinitely greater than the sum of its parts.

Then I saw the dissonance appear. Bob had chosen to show it as a sullen red light that began to pulse lightly at the westernmost edges of the great design. It began as something faint, but then, like an oncoming headache, started to throb into something larger and more noticeable. Where scarlet and blue light touched, there were ugly flares of energy-flares that I had been sensing ever since I'd gotten to the island. Before long, that scarlet pulse had spread to half the island, and then, abruptly, the screen went white.

Text at the bottom read, NOVEMBER 1.

"By tomorrow," I said. "Super. But I still don't see what is wrong, Bob."

"Energy hits it," Bob said. "A directed burst of energy, a whole lot of it. It unravels the whole containment spell Merlin laid down and triggers the fail-safe."

"FIRE," rumbled Demonreach.

"I figured that one out, thanks," I said. "But nothing has actually happened to the spells yet?"

"Nope," said Bob. "That tension that's building? It's . . . Well, think of it as cause and effect, only backward."

"Huh?"

"What the island is experiencing now is the echo of the moment that burst of energy strikes it," Bob said. "Only instead of the echo happening after, it's happening first."

I stopped and thought. "You're telling me that the reason the island is about to blow up is . . . because it's about to blow up?"

Bob sighed. "Someone hits the island with energy, Harry. But they've figured out how Merlin put this place together. They aren't attacking it in three dimensions. They're attacking in four. They're sending power through time as well as through space."

"So . . . I have to stop them from attacking the island tomorrow?"

"No," Bob said, exasperated. "You have to stop them from attacking whenever it is that they actually attack."

"Uh . . ."

"Look, the rock they're throwing hits tomorrow," Bob said. "But you have to stop them from throwing it at whatever point they're standing when they throw it."

"Oh," I said, blinking. "I get that."

Bob turned to look at Demonreach. "Do you see what I have to work with here? I had to take that down to throwing a rock before it got through."

"HIS UNDERSTANDING IS LIMITED," Demonreach agreed.

"Okay, I've had just about enough from both of you," I said. "If you're so smart, how come you don't stop it from happening?"

"THE EXPLANATION WOULD DAMAGE YOU, WARDEN."

Bob made an impatient sound. "Because that spirit is the island, Harry. The spells, the Well, the physical island, all of it. Demonreach does not exist outside this island. It has no ability to reach beyond itself. The attack is coming from outside the prison. That's why it needs a Warden in the first place."

I scowled. "It talked to me in the graveyard last year."

"It bullied Mab into helping it," Bob said.

"I DID NOT BULLY. I BARGAINED."

"Okay, okay," I said. "I'll add that to my list, then. Find whoever it is, wherever they are, and stop them from doing something they haven't done yet."