"Has one of you got a silver knife?"

"Yep," Kate said, distracted as she worked the last of the yale horn in to powder, sliding it across to Lucy and measuring out half a cup of water. The fire was already hot, and once Dan finished with his own yale horn, she got him to start on his water, too.

"Right," she told him, "Once this is boiling, make sure we have all of our ingredients ready, since we need to add these pretty quickly. We add four drops of Valentine Water and boil it for two minutes, then bring it down to a simmer. Then we need to add - quickly - the moonstone, then the ironwood nut pieces - Noah, you can cut it - then a mix of ambrosia extract and yale horn. The ambrosia and yale horn needs to be stirred three times clockwise, nine times anticlockwise."

Dan grinned. "Ready! Sure I can't make anything explode? Kate gave him a pointed look, one that had actually managed to calm Luke down, and he settled. Tugging the moonstone and nut off Noah, he brought the water to boil, adding in four drops of Valentine Water - Kate counted them off and added her own.

In the two minutes it took for the potion to continue boiling, she instructed the boys in combining the extract and the horn in a seperate bowl, showing them how to stir it properly while Lucy prepared theirs. Then, lowering the potion to a simmer, she added, "Okay, here's the tricky part. That blue's fine - add the moonstone."

She carefully measured out half a teaspoon and added it to her own potion, checking that the boys did the same. Grey steam wafted off, and she smiled in satisfaction. "Now the nut," she continued, and Lucy dropped their pieces of nut in to their own potion. The blue deepened, the steam fading. "Aaand now the mixture."

Dan added it, dropping a little over the side and scooping it up with a finger, brushing it off. The potion was royal blue, now, fine white mist settling over it.

Kate grinned, relieved that nothing had exploded. "Now there's twenty-two minutes while it cools. Well done, guys."