Without another word, the adults ran through the gate and down the spiral road. Little Bear sat on his rump and, began to howl.

Three more boom-stones exploded overhead. Tris flinched at each one; her hair began to rise and crackle. She tucked her hand into her pocket, and rubbed Aymery's earring.

They had to distract Tris, before something else happened, thought Daja. "What if you tried your lightning on that?" She pointed to the heap of black powder that lay forgotten in the path.

Tris stared at it. "I - I don't know," she said, her voice trembling.

"Well?" Sandry nudged.

"What lightning?" Briar demanded, sarcastic. "She's just got the worst case of Runog's Fire I've ever seen, is all."

Daja knew the pale fire that played on ship masts and tower roofs in storms as well as he did. "What she's got is seed lightning," she returned. "It's not the same. Show him, Tris."

Another boom-stone exploded over the Hub. "I c-c-can't," Tris replied, shivering with fright. What did they want from her? Couldn't they see that each explosion felt like a sharp blow to her? Her muscles were clenched, awaiting the next strike, and her neck and back were aching.

"Don't you have to learn control?" Sandry asked. "No matter what else is going on? Maybe this is a good time to practise."

Tris glared at the other three, hating them for bothering her. She just wanted to run inside and hide under a bed.

"Ahhh, I knew it," Briar remarked scornfully. "It's just Runog's Fire."

Furious, Tris pointed to the heap of powder a foot away. Lightning jumped from her finger. There was a clap: dirt and smoke sprayed everywhere, blackening them and turning the observing Little Bear grey. The dog yipped, and fled into Discipline. The four looked at each other, eyes wide in soot-streaked faces. There was now a hole in the path.

"You see?" Briar said at last. "You just have to know what to say to her."

"You -" Tris snapped, and pointed at him without thinking what might result.

Briar grabbed her arms, hard, shaking her as lightning-sparks raced over his hands. "Don't you ever do that," he whispered, his eyes burning into hers. "Don't you ever. If your pointing is a weapon, then don't you point 'less you're ready to kill with it. You understand, you witless bleater?" He was so frightened he didn't know where his trembling ended and hers began. "Niko's right." He let her go and pushed her away from him. "We got to learn control, and you most of all."

"I'm sorry." Tris's eyes were spilling over, but she made herself look Briar in the face. "I'm sorry. I didn't - I wouldn't ever -"

Sandry put her arm around Tris's shoulders. "We can't just act without thinking any more, Tris. They've been trying to teach us that all along. I guess if we're mages, we can't exactly be kids, can we?" she asked the other two. They shook their heads. "Briar knows you would have been sorry after."

"After I was a nice crispy roast just off the spit," the boy said cruelly.

Tris hid her face in her hands.

"Enough," Daja said. "She got the point. Don't bully her."

I'm a scared bully, thought Briar, stuffing his hands into his pockets. And I want to be sure she's scared, scared enough to think next time.

Tris yanked out of Sandry's hold and ran up to her room.

Briar went to examine the miniature pine tree that sat on his window-ledge, letting the shakkan's years and plant-calm steady his nerves. Checking the dirt in its shallow basin, he decided it was a bit dry, and went inside for water.

Daja and Sandry stayed where they were, staring at the hole in the ground.

"What do you suppose her reach is, with lightning?" Daja enquired. "Could she hit a boom-stone?"

Sandry tugged one of her braids. "I don't know. Remember the day we all first met? Lightning struck a tree outside Administration when we were there. I think that was her - she was angry; I could tell the moment I laid eyes on her. And she wasn't excited by lightning hitting so close to her. But it was stormy that morning. This lightning just seems to cling to her - it's not part of a storm. It might not reach as far."

"But when she holds on to it, it grows. Remember? It starts as a spark. Then she holds it, and it grows into a strip." Daja scuffed at the dirt around the hole.

"I think we should find out how far she can send it."

Sandry bent down and petted Little Bear, who had crept out of the house again. "I think you're right," said Daja.

The safest place appeared to be the lee of the northern wall beside Discipline. There was a broad strip of grass with no other plants growing there - Briar had refused to allow an experiment anywhere in Rosethorn's garden. Only the sentries could see them, but for the most part they were looking out to the north, or to the south, where the burning buildings were. By now the word had come up the road: a boom-stone had got through the magical barriers, exploding in one of the large buildings that housed Winding Circle's carpentry shops. There were dead and wounded, and people trapped inside. It would be a while before their teachers could be spared from rescue work.

Once Briar had been converted to the idea of lightning experiments, he made some reed circles for use as targets. Sandry dug in Lark's scrap bag, and brought out a number of cloth patches which she placed in different spots. Daja's assignment was to get Tris to go along.