How do I make a cone reveal a material?

Hello All,

I’m trying to make a translucent character that, when a flashlight is pointed at them, the part of them that is hit by the light becomes opaque, but the rest of the character is still translucent.

Example: a flashlight is pointed at the character’s legs - the legs are visible but the torso is not.

I found a video that looks like it does something similar, but I could not find an explanation on how to do it nor could I find it for sale on the marketplace.

Here is the video: - YouTube

Any advice would be greatly appreciated. Thank you!