What Am I doing Wrong

//Problem: User when clicking on image goes to a dead end
//Solution: Create an overlay with the large image - Lightbox

var $overlay = $('');
var $image = $("");
var $caption = $("");

//An image to overlay
$overlay.append($image);

//A caption to overlay
$overlay.append($caption);

//Add overlay
$("body").append($overlay);

//Capture the click event on a link to an image
$("#imageGallery a").click(function(event){
  event.preventDefault();
  var imageLocation = $(this).attr("href");
  //Update overlay with the image linked in the link
  $image.attr("src", imageLocation);

  //Show the overlay.
  $overlay.show();

  //Get child's title attribute and set caption
  var captionText = $(this).children("img").attr("imageGallery");
  $caption.text(captionText);
});

//When overlay is clicked
$overlay.click(function(){
  //Hide the overlay
  $overlay.hide();
});