Lightbox-style slideshow (from only ONE link)

I want a jQuery (or similar) plugin script to display a selection of images in a lightbox-style slideshow, to be scrolled through by the viewer. I need a slideshow that is not dependent on images linked from the HTML.

I have three groups of 5 or 6 photos, each of which is represented by only one thumbnail in the HTML (i.e. only three thumbnails on the page). Clicking on each thumbnail must launch the gallery group with which that thumbnail is associated. The HTML should not contain any direct links to the full-size images, so they must be fetched by the script. Full keyboard accessibility is essential.

Basically this is quite like the kind of slideshow that is often seen on photo gallery services (e.g. Zenfolio, Smugmug, etc.), which is launched from a single link without necessarily relating to images on the page. The usual lightbox solution of placing a list of links to all of the images in the HTML and having as many links or thumbnails as there are photos is not at all suitable in this instance.

I really hope that someone can suggest the right solution.