White could move his queen to the bottom of the board in view of both the black king and the rook, checking the king. The rook is then forced to kill the queen, which allows the white king to move closer to the black knight. The black player is then forced to move the knight away, or just move the rook back to where it was. If the latter, the king can kill the knight, and have only the rook to deal with. That's the best I could come up with.
Were you white, Hans? and did you win?