Halo: Number 1 in series

Three angels are sent down to bring good to the world: Gabriel, the warrior; Ivy, the healer; and Bethany, a teenage girl who is the least experienced of the trio. But she is the most human, and when she is romantically drawn to a mortal boy, the angels fear she will not be strong enough to save anyone-especially herself-from the Dark Forces. Is love a great enough power against evil?