Fair Game by Patricia Briggs (2012) Ace

We follow the werewolf enforcer and his wife as they work on the mysterious deaths of three werewolves.  When they get to Boston, there is a currently missing fae, the half-human daughter of one of the ruling lords of the fae.  Our werewolves find her, but she has been hurt badly and will never be able to dance again.  The people responsible are brought to trial, but are declared not guilty by a jury.  The fae lord, declares that the fae are no longer at peace with the U.S. and decapitates the guilty party.