diff --git a/classes/ComicPressComicPost.inc b/classes/ComicPressComicPost.inc
index b10f7d1..7b3c74d 100644
--- a/classes/ComicPressComicPost.inc
+++ b/classes/ComicPressComicPost.inc
@@ -187,9 +187,9 @@ class ComicPressComicPost {
         sort($ids);
         $requested_order = array_merge($requested_order, $ids);
       }
-      
+
       $requested_order = array_merge($requested_order, array_diff($current_order, $requested_order));
-      
+
       foreach ($requested_order as $requested_comic) {
         if (in_array($requested_comic, $current_order)) {
           $new_order[$type][] = $requested_comic;
@@ -199,7 +199,6 @@ class ComicPressComicPost {
     
     update_post_meta($this->post->ID, 'comic_ordering', $new_order);
   }
-  
 }
 
 ?>
\ No newline at end of file
diff --git a/classes/ComicPressNavigation.inc b/classes/ComicPressNavigation.inc
index 34a6c91..9f14b39 100644
--- a/classes/ComicPressNavigation.inc
+++ b/classes/ComicPressNavigation.inc
@@ -1,37 +1,7 @@
 <?php
 
 class ComicPressNavigation {
-  function init($post, $storyline) {
-    $this->post      = $post;
-    $this->storyline = $storyline;
-  }
-  
-  /**
-   * Find the terminal post in a specific category.
-   */
-  function get_terminal_post_in_category($category_id, $first = true) {
-    $sort_order = $first ? "asc" : "desc";
-    $terminal_comic_query = new WP_Query();
-    $terminal_comic_query->query("showposts=1&order=${sort_order}&cat=${category_id}&status=publish");
-    if ($terminal_comic_query->have_posts()) {
-      return reset($terminal_comic_query->posts);
-    }
-    return false;
-  }
-  
-  /**
-   * Get the first comic in a category.
-   */
-  function get_first_in_category($category_id) {
-    return $this->get_terminal_post_in_category($category_id);
-  }
-  
-  /**
-   * Get the last comic in a category.
-   */
-  function get_last_in_category($category_id) {
-    return $this->get_terminal_post_in_category($category_id, false);  
-  }
+
 }
 
 ?>
\ No newline at end of file
diff --git a/classes/ComicPressStoryline.inc b/classes/ComicPressStoryline.inc
index 513989d..f6e1c83 100644
--- a/classes/ComicPressStoryline.inc
+++ b/classes/ComicPressStoryline.inc
@@ -1,5 +1,7 @@
 <?php
 
+require_once('ComicPressDBInterface.inc');
+
 class ComicPressStoryline {
   var $_structure;
   
@@ -72,7 +74,7 @@ class ComicPressStoryline {
     }
     return is_array($this->_structure);
   }
-  
+
   function _get_field($field, $id) {
     if (isset($this->_structure)) {
       if (isset($this->_structure[$id])) {
@@ -96,18 +98,31 @@ class ComicPressStoryline {
     return false;
   }
 
+  /**
+   * Get the valid navigation directions for a particular post.
+   */
   function get_valid_nav($post_id) {
-    $data = false;
+    if (($category = $this->get_valid_post_category($post_id)) !== false) {
+      return $this->valid($category);
+    }
+    return false;
+  }
 
+  /**
+   * Get the valid comic category for this post.
+   */
+  function get_valid_post_category($post_id) {
+    $result = false;
+    
     foreach (wp_get_post_categories($post_id) as $category) {
-      if ($result = $this->valid($category)) {
-        if ($data) { return false; }
+      if ($this->valid($category)) {
+        if ($result) { return false; }
 
-        $data = $result;
+        $result = $category;
       }
     }
-    return $data;
-  }  
+    return $result;
+  }
 }
 
 ?>
\ No newline at end of file
diff --git a/test/ComicPressStorylineTest.php b/test/ComicPressStorylineTest.php
index 51a06a2..52d2d38 100644
--- a/test/ComicPressStorylineTest.php
+++ b/test/ComicPressStorylineTest.php
@@ -134,6 +134,26 @@ class ComicPressStorylineTest extends PHPUnit_Framework_TestCase {
 
     $this->assertEquals($expected_navigation, $this->css->get_valid_nav(1));
   }
+
+  function providerTestGetValidPostCategory() {
+    return array(
+      array(array(1,2), false),
+      array(array(1,3), false),
+      array(array(1), 1),
+    );
+  }
+
+  /**
+   * @dataProvider providerTestGetValidPostCategory
+   */
+  function testGetValidPostCategory($post_categories, $expected_result) {
+    $css = $this->getMock('ComicPressStoryline', array('valid'));
+    $css->expects($this->any())->method('valid')->will($this->returnValue(true));
+    
+    wp_set_post_categories(1, $post_categories);
+
+    $this->assertEquals($expected_result, $css->get_valid_post_category(1));
+  }
 }
 
 ?>
\ No newline at end of file