It’s black’s move: The Spy, by moving next to the rook, has made the rook and itself into checking pieces. But the King, now under attack, can capture the rook, as long as it is not protected by another piece

(the Spy is an exception). By capturing the rook and moving next to the Spy, Black wins via the flipping rule. If a white bishop were also a colluding piece, being on, say, e8, the King could not capture the rook.