After falling into a parallel world, Rosie meets Katie and is drawn into a search for her own double Rosy. Together with Troad Glim and Kit they travel to Icara to seek the help of Queen Meraic. The help comes in the form of Commander Elbert and one hundred elvin soldiers. Now they must travel to the mine to rescue Rosy and prevent Weevil and Weedle from releasing Crowvan the wizard and his dragon Midnight from beneath the Dark Mountain.
Meanwhile, after being kidnapped by Weevil and Weedle Rosy meets Tom and along with others are rescued by a gang of boys led by Geordie. Rosy and Tom join the gang but if they are to free all of the slaves they must carry out an attack on the mine itself. During the attack things go wrong, but Rosie Katie and the elvin troops arrive just in time to prevent them being overwhelmed. The goblins are routed and the slaves are freed.
Now all that remains is to winkle out Weevil and Weedle from inside the mine and prevent the release of the wizard and his dragon.