The Sound of Seas Book 3 of The EarthEnd Saga

After discovering the secrets to the Gaalderkhani tiles--ancient computers that house not just memories, but untold destructive force--Caitlin O'Hara's son gets accidentally thrust back in time. In order to save him she must master the power of the tiles and figure out what the Gaalderkhani's modern relatives are searching and killing for. Can she put the pieces together and bring her son back home again?