When it was complete, she took her hands away. "It'll be stronger when we join," she told her companions.

Tris closed her eyes, calling to her original protection. The lightning poured over Sandry's wall in a stream of white heat to pool in the redhead's cupped palms. When she had retrieved all of it, she rolled it into a fiery ball, and put it on the wall in front of them.

Closing their eyes, the four came together as they had once done in the middle of an earthquake, to become one. Daja was not sure that she liked such closeness. Briar felt the same way. Sandry brushed them with soothing warmth, reminding them that it was just for the moment, then turned her attention to the moon-pale wall that she had built. Touching it with their joined strength, she made it blaze.

Let's get to it, Tris said.

Not so fast, replied Daja. Weren't you listening? There are mage-traps in the barrier. If we attack it, let's make sure we don't strike one.

We don't even know what they look like, Sandry argued.

Just look at it, Briar told her. We've been seeing magic for days, so let's find out if we can spot differences in the stuff.

Leaving their bodies on the wall, the four went to the magical shield. Sandry hunted for changes in its weave, Tris for storm centres, Daja for rust spots. From his long experience in climbing garden and house walls, Briar knew better than to trust his eyes: Bags always paid extra for spells to hide other spells. Flinging his mind forward, the ex-thief went over the silvery wall an inch at a time, poking it with a finger.

Here, he said at last. And here, and here.

We don't have to look more, Tris pointed out. If we hit the barrier in the middle of those spots, we might break through.

Let your waterspout spin us together, Daja suggested. To make us stronger. When we come out through the top, we'll fly at that place.

Briar left a dab of green fire to mark their target. The four drifted to the top lip of the waterspout as it whirled before the pirates' barrier.

Looking at the funnel, Briar said approvingly, You've got a monster this time, Coppercurls.

Let's go! Tris cried, and let herself fall into the outside of the spout. The others followed, wrapping themselves around her. The floods that whipped along the funnel's sides grabbed them, twirling them around and around as wind and water carried them down to the sea. They could feel themselves being wound ever more tightly into one being.

Daja felt heat as well, the heat of a forge-fire, warming them, making them blend together easily. How much more of their power would leak between them if they survived this? There was no chance to really consider it - they rushed madly into the pointed end of the funnel, and were sucked inside. Now the current bore them up through the spout, speeding them up.

Just a bit more, thought Tris as they neared the top. A little more, a little...

They shot out of the spout's top, and slammed into the barrier at eyeblink speed. Something before them gave. The barrier's magic no longer felt like a smooth and solid whole.

Again, decreed Sandry.

They returned to the waterspout, soaring into its outside current and letting it yank them down. It too was spinning faster, twirling the four wildly. They felt powerful and furious. Shooting out of the top, they leaped away to arrow at the green spot Briar had left for them.

The entire barrier shattered like glass. In roared the waterspout, to fall on a galley in the front ranks of the fleet. Chunks of wood went flying as it bit into the port oars. The four broke apart, ready to get to work.

Briar looked back. There were bare, charred patches on the shore where battlefire had devoured the brambles that he and Rosethorn had worked so hard to grow. Now a single longboat was drawn up on the blackened slope, its load of pirates already ashore. They were throwing skins of battlefire on to the remaining thorns and setting them ablaze, making room for even more invaders to land. A pair of men who glinted with magic shielded them from the spells of Winding Circle's defenders.

The boy glanced at the top of the wall. There was the glow of Sandry's protective barrier, with the four's real bodies just visible through a notch in the stone. Most of the soldiers and mages who had encircled them were gone, manning the walls and catapults against the pirates labouring on the beach. He couldn't find Skyfire's shock of red hair, but it was a long trot from Discipline to the South Gate: the general would be there soon, he had no doubt. Skyfire would be needed - in the cove seven more longboats filled with armed pirates and their protector-mages waited for room enough to land.

Briar was not about to permit that, any more than Winding Circle's defenders were. He sank into the earth, drawing on the link between him and the girls for the power to regrow his brambles.

Daja circled a galley. Where to start? The metal on its catapult looked promising.

She thought back to that morning - just yesterday! - in the harbour. Right before Frostpine had raised the chain she had felt a thin shiver in the air, like a razor drawn down a bone. She called that shiver out of herself now, putting the strength of her link to the other three in it. She invited dull metal to fly.

Wood squeaked as nails fought to escape it. Weapons rose, yanking from their masters' holds. Metal fittings worked themselves off the ship, and soared into the air. She drew all of it over to the ship's lee, then let the metal fall into the water. Section by section, she went over the ship, leaving ruin in her wake.

Suddenly she had to catch her breath. Opening her real eyes, Daja squinted to see through the white light of their barrier. Only a couple of soldiers remained just outside, keeping one nervous eye on the four, and the other on the shore below. The South Gate mages, led by Moonstream, defended the cove against a pirate landing-party. Other initiates had moved into every spot along the wall that gave a view of the invaders. They knew the fleet's magical barrier was down. As Skyfire stalked to and fro on the wall shouting orders and calling out targets, everyone who could throw fire, or make ropes or chains come to life, or pop lanterns from holders, was at work. Invisible hands shoved raiders overboard. Oars on neighbouring ships fouled one another.