The Mountebank

The Wizard King of Conyor Ness sends his two best Relays, his daughter and son, Prince Nikari and Princess Nikeri, twins, to the Amethyst court to protect the Princess's ringfasted from an assassin. But someone seems determined that they will never make it.
Worn from their last Relay adventure, armed with scrying discs, the twins work to discover who their attacker is before they reach the Amethyst palace and before its too late.