Having saved the first Shard of the sword Excalibur from Internet mogul Rex Major (aka Merlin), Ariane and Wally are on the lookout for the second. Wally's worried that the power of the first Shard is already changing Ariane, giving her the strength to do good and evil--and when she seriously hurts his bullying sister, Flish, it seems he's right. Meanwhile, they have a serious problem: Ariane's located the second Shard in France. Sure, her inherited powers from the Lady of the Lake enable her to travel magically through fresh water, but it hasn't escaped their notice that there's a huge saltwater ocean separating them from their next target. And Rex Major is already on his way there.

As Major uses Wally's doubts--and his secret wish to be more than just a nerdy sidekick--to cause a rift between the friends, Ariane takes the chance to go it alone. But if the first Shard's power is barely controllable, how will she fare when two Shards are united? And what can Wally do to get his friend back?