Clicking on the pdf links from the[1] home page will give you a number of errors that indicate specific files can not be found. If you click on the Network Theory pdf link it will give you the following page linked from

Not Found

The requestedted file Abigail.txt was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

If you then go to you will get the following simple text file:

Queen of Hearts.

If you look at the last three words they begin with joyful, playful and games suggesting the extension jpg. By using that with the previous phrase you can find of Hearts.jpg [2]