Plot: For the first time in Voice history, the coaches enlist not one, but two Grammy Award-winning artists and country music sensations Tim McGraw and Faith Hill to serve as a key advisers and be on hand to work with all of the coaches and their teams as they prepare the artists for the Knockout Rounds. The Knockout Rounds begin with coaches Miley Cyrus, Alicia Keys, Adam Levine and Blake Shelton's strongest team members remaining from the battle rounds