Images In Javascript Popover Plugin

Having just reinstalled WP, I want to use the excellent plugin that provides a javascript window with the image in when a thumbnail of the image is clicked. I remember it doing it automatically if the thumbnail is linked to the image itself, but when searching for it I can only find ones that require adding extra tagging, which is not what I’m looking for.

The only other thing I can remember is that the plugin shows each image in a white box and darkens the rest of the page.