Gatekeeper

Rachel Wilde comes from a dimension that exists adjacent to ours. Now Rachel has been given two unusual assignments: 1) find a person who has been trying to break down dimensional barriers, and 2) track down a missing line of gatekeepers, human placeholders for a daemon that was too badly damaged to repair. The people there have structured their society around daemon collecting: they locate, catch, and repair malfunctioning daemons (creatures out of phase with our world that tempt people to do good or evil).

With no leads to go on, Rachel seeks help from Bach, a raving homeless man who happens to be an oracle. Authorities of Rachel's world believe the missing gatekeepers are descended from a girl who went missing from West Africa hundreds of years ago, likely sold into slavery. Bach does put her in the path of both of her targets--but he also lands her in a life-threatening situation.