The shadow matrix

Margaret, heir to the Alton Domain, is marked with a mysterious power symbol that even the sages don't understand. To make matters worse, she is at the center of a political struggle, forbidden to marry her true love Mikhail, regent to the Elhalyn Domain. When the lovers are drawn to an ancient Tower, they are sent back through time, awaited by a dread Keeper, who sends them on a perilous quest.