The Crosses are back in book 7 of the Out of Time Series.
An old enemy returns threatening to destroy not just Simon and Elizabeth but the timeline itself. To keep that from happening, they travel back to 1888 London to find Jack the Ripper…and save his life. If he dies, the timeline changes, everything they know and their lives together, will be lost. But they soon discover the only thing harder than saving a monster is finding him.