newbie: using sketches to outline plane

i have a plane object which i have applied a sketch material in order to give it a black outline. i have a video as my background scene. before i apply the sketch material my renderings are fine, but after i apply the sketch the background turns white and my background video dissapears. Would anyone know what I am doing wrong or is there another way to achieve an outline that will not take my background out.

Thanks so much,
vikas