It was the chanciest bit of the plan, because the existence of this secret back passage was a matter of speculation, but whatever, if it didn’t work she’d find some normal, less dramatic way to corner him.

She looked quickly over her shoulder—Coldwater still out of view and/or otherwise engaged—then knelt by the wainscoting. She took a deep breath. Third panel from the left. Hmm—the one on the end was half a panel, not sure whether she should count it or not. Well, she’d try it both ways. She traced a word in Old English with her finger, spelling it out in a runic alphabet, the Elder Futhark, and meanwhile clearing her mind of everything but the taste of a really oaky chardonnay paired with a hot-buttered toast point.

Lemon squeezy. She felt the locking spell release even before it happened: the panel swung outward on a set of previously invisible hinges.

Annoyingly though, the passage had been sealed. Ten feet in it ended in a brick wall, and the bricks had been bricked in such a way as to form a design that Plum recognized as an absolutely brutal hardening charm—just a charm, yes, but a massively powerful one. Not undergraduate stuff. Some professor had bothered to put this here, and they’d spent some time on it too. Plum pursed her lips and snorted out through her nose.

Crouching down, she stepped into the passage and pulled the little door shut behind her. She snapped on a simple light spell, a friendly glowy will-o’-the-wisp. Then she stared at the brick wall for five minutes, in the dimness of the little passageway, lost to the world in an analytical trance. In her mind the pattern in the bricks floated free and hung before her all on its own, pure and abstract and shining. Mentally she entered the pattern, inhabited it, pushed at it from the inside with cognitive fingers, feeling for any sloppy joins or subtle imbalances.

There must be something. Come on, Plum: it’s easier to break magic than to make it. You know this. Whoever drew this seal was smart. But was she smarter than Plum?

There was something odd about the angles. The essence of a glyph like this wasn’t the angles, it was the underlying topology—you could deform it a good deal and not lose the power as long as its essential geometric properties remained intact. The angles of the joins were, up to a point, arbitrary.

But the funny thing about the angles of these joins was that they were funny. They were sharper than they needed to be. They were nonarbitrary. There was a pattern to them, a pattern within the pattern: 17 degrees, 3 degrees. Seventeen and three. Two of them here, two of them there, the only angles that appeared twice.