It's summertime, and that means camp for the twins! While Claire loves-loves-loves all sports, Luna would rather hide out in the infirmary. Luckily, Grandy has given Luna some marigold powder so that she'll have more zest for camp. But when the powder disappears and strange things start to happen at Camp Bliss, the twins must hunt down the rebel witch who's been sprinkling zest where it doesn't belong.