There are precisely two lights in this image, an infinite--for a general soft illumination--and a spotlight, pointing at the figure. The woman's shadow is cast by the spotlight--the shadow moves (the pair of them, together) when I move the light. But there are two overlapping shadows. Why? I can see no difference in the way the light is set up from my usual set. It is like the lady has an invisible (but shadow-casting) doppelganger just behind her. The shadow is ray traced.  There are no other haunting figures in the scene, no other forgotten lights.

I dont mind the effect, I think it is rather interesting, but I would really like to know how this happened!

larger shadow drops off towards camera, as if it's shadow-mapped with too little coverage, when viewed in shadowcam.

I can not tell for sure, but do you have both the ground plane and the floor in the scene at different y coordinates? Bill

Willyb, that was it...the ground plane was catching a shadow too...it is higher than the cobbled floor. I just made it invisible, and the doppelganger's shadow vanished.

And Nancy, I just looked thru the shadow cam, and you were right. I aimed the light a bit lower, and now the shadow begins right at the foot.

Thank you both!