Terrier: A Tortall Legend (Beka Cooper, Book 1)

Several hundred years before Alanna decided she wanted to be a knight, there was a young woman with magical gifts who decided she wanted to be part of the provost guard. She was apprenticed to two of the most experienced 'dogs,' and the three of them prowled the streets of Corus to be sure justice prevailed even in poorest parts of the city. Beka Cooper can hear the ghosts of the dead, as they ride on the backs of pigeons. She learns that someone is blackmailing folk who own something valuable, and then killing their offspring, if they don't pay the ransom to get them back. These are dark times, and shy Beka is just finding her gifts and coming of age. Bloodhound is the sequel to this book.