How to Make a Shadow "On the Background"

I am animating a character who is in front of a video. I inserted it in the VS Editor, and added the alpha under effect. That is working fine, except I can’t figure out how to make it give off a shadow without having a plane in my scene. Is there a way to make a plane alpha and still receive shadows?


Mark the plane ‘Only Sha’ - 2.49

or ‘Shadows Only’ - 2.53