Jeff Schrattner scored the Siskin's lone goal as Waterloo lost 5-1 to London in Game 6 of the Sutherland Cup final.
Noah Tooke opened the scoring just over a minute into the game and Max Vinogradov put the Nationals up 2-0 at 14:14 of the first period.
James Turner made it a 3-0 game just over three minutes into the second. Schrattner put the Siskins on the board about two-and-a-half minutes later.
A power play goal by George Diaco before the midway point of the middle frame game the Nationals a 4-1 lead heading into the final period.
Christian Polillo scored the Nationals' final goal at 3:03 of the third.
Polillo, Diaco, Turner, Tooke and Vinogradov all scored and had an assist in the win and Zachary Springer made 36 saves.
The Siskin's Matt Onuska made 26 saves on 31 shots before being replaced by Machus Turner early in the third. He stopped all 10 shots he faced.
Game 7 is Wednesday in London.
