Masked template on desktop. cannot remove
I updated my Mac Mini this morning and somehow I have ended up with a masked template over my home screen. I have tried restarting and it won't go away. I have nothing open right now so it isn't coming from a program. Can anyone tell me how to get rid of this. The screenshot I took does not show the template. I have attached a photo I took with my iPhone.
Mac mini, OS X Yosemite (10.10.3)