Using a node reference in Drupal 7, is there a way to tell what the parent node is?
Reading the text of your question, it looks like you don't necessarily need to know what the parent is but more where the visitor is coming from (and if it is a movie which one).  

A possible solution, as you mentioned, would be to add some parameters to the URL.  A simpler option might be just a tiny bit 'o javascript.

&lt;script type="text/javascript"&gt;
  (function ($) {
    $(document).ready(function() {
      var referrer =  document.referrer;
    });
  })(jQuery);
&lt;/script&gt;


Then use the referrer (previously browsed URL) and compare it against the list of movie URLs via JQuery.  If one matches, add a css class to style the link as an indicator.

&lt;script type="text/javascript"&gt;
  (function ($) {
    $(document).ready(function() {
      var referrer = document.referrer;
      $('#movie-list li a').each(function(index) {
        if ($(this).attr('href') == referrer) {
          $(this).addClass("active-movie");
        }
      });
    });
  })(jQuery);
&lt;/script&gt;


Where

&lt;ul id="movie-list"&gt;
  &lt;li&gt;&lt;a href="http://example.com/duck"&gt;duck&lt;/a&gt;&lt;/li&gt;
  &lt;li&gt;&lt;a href="http://example.com/duck"&gt;duck&lt;/a&gt;&lt;/li&gt;
  &lt;li&gt;&lt;a href="http://example.com/goose"&gt;goose&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;