Index: wp-includes/template.php
===================================================================
--- wp-includes/template.php	(revision 24887)
+++ wp-includes/template.php	(working copy)
@@ -366,7 +366,11 @@
  * @return string The template filename if one is located.
  */
 function locate_template($template_names, $load = false, $require_once = true ) {
-	$located = '';
+	$located = apply_filters( 'locate_template_override', '', $template_names, $load, $require_once );
+
+	if ( $located )
+		return $located;
+
 	foreach ( (array) $template_names as $template_name ) {
 		if ( !$template_name )
 			continue;