After 9.Bf4, play could proceed as 9...g6 10.Nd4 Nge5 (Nxd4)11.Bxe5 de (11...fe 12.Qf3) 12.Nxc6 Qxd1+13.Rxd1 bc 14.Nb5 ! FIG. 26 Black must lose his rook to avoid mate.