Music in the Night - Michelle L. Levigne

Ess's mother, Vivian, left her a rose made of the same crystal that formed the Great Machine, which allowed the Originators and Revisionists to travel through time. A matching rose belonged to her friend, Anna, and the two women communicated mind-to-mind, until Vivian died. When Ess was too young to understand, she touched minds with Carmen, Anna's daughter, through the crystal rose. Both girls thought the other was merely an imaginary friend.

Now, knowing the truth, Ess must search for Carmen, who is in great danger from the Revisionists. Anna died before she could teach her daughter the truth of the crystal rose, and her heritage. Carmen has no idea what gifts lie in her blood, in the power of song, and in the crystal rose.

When one piece of bad luck after another puts Carmen and her orphan charges out on the streets, they find shelter in an underground community. Their leader, Brogan, hides his scars in the shadows, and fears he is slowly growing insane. Carmen's music may be the key to solving puzzles passed down from their ancestors. The fate of the world of the future could rest in their hands.