diff --git a/classes/ComicPressDBInterface.inc b/classes/ComicPressDBInterface.inc
index 71b07d0..b47b3c5 100644
--- a/classes/ComicPressDBInterface.inc
+++ b/classes/ComicPressDBInterface.inc
@@ -106,6 +106,19 @@ class ComicPressDBInterface {
 	function get_next_post($categories = null, $override_post = null) { return $this->get_adjacent_post($categories, true, $override_post); }
 
 	// @codeCoverageIgnoreEnd
-}
 
-?>
+	function get_parent_child_category_ids() {
+		global $wpdb;
+
+		$parent_child_categories = array();
+
+		$result = $wpdb->get_results("SELECT term_id, parent FROM $wpdb->term_taxonomy", ARRAY_A);
+		if (!empty($result)) {
+			foreach ($result as $row) {
+				$parent_child_categories[$row['term_id']] = $row['parent'];
+			}
+		}
+
+		return $parent_child_categories;
+	}
+}
diff --git a/classes/ComicPressStoryline.inc b/classes/ComicPressStoryline.inc
index cf64314..e39c0c4 100644
--- a/classes/ComicPressStoryline.inc
+++ b/classes/ComicPressStoryline.inc
@@ -247,19 +247,28 @@ class ComicPressStoryline {
 		return $this->_merge_simple_storyline($simple_storyline);
 	}
 
+	function get_comicpress_dbi() {
+		return ComicPressDBInterface::get_instance();
+	}
+
 	/**
 	 * Get a simple structure.
 	 */
 	function get_category_simple_structure($parent = null) {
 		$structure = array();
-		foreach (get_all_category_ids() as $category_id) {
-			$category = get_category($category_id);
-			if (!isset($structure[$category->parent])) {
-				$structure[$category->parent] = array();
+		$dbi = $this->get_comicpress_dbi();
+
+		$result = $dbi->get_parent_child_category_ids();
+
+		foreach ($result as $cat_id => $cat_parent) {
+			if (!isset($structure[$cat_parent])) {
+				$structure[$cat_parent] = array();
 			}
-			$structure[$category->parent][$category_id] = true;
+			$structure[$cat_parent][$cat_id] = true;
 		}
+
 		$structure = $this->_merge_simple_storyline($structure);
+
 		if (!empty($parent)) {
 			if (isset($structure[0])) {
 				foreach ($structure[0] as $key => $children) {
@@ -267,6 +276,7 @@ class ComicPressStoryline {
 				}
 			}
 		}
+
 		return $structure;
 	}
 
diff --git a/test/ComicPressStorylineTest.php b/test/ComicPressStorylineTest.php
index e254440..9449c0b 100644
--- a/test/ComicPressStorylineTest.php
+++ b/test/ComicPressStorylineTest.php
@@ -283,11 +283,15 @@ class ComicPressStorylineTest extends PHPUnit_Framework_TestCase {
 	}
 
 	function testGetCategorySimpleStructure() {
-		add_category(1, (object)array('parent' => 0));
-		add_category(2, (object)array('parent' => 1));
-		add_category(3, (object)array('parent' => 2));
-		add_category(4, (object)array('parent' => 2));
-    add_category(5, (object)array('parent' => 0));
+    $css = $this->getMock('ComicPressStoryline', array('get_comicpress_dbi'));
+
+    $dbi = $this->getMock('ComicPressDBInterface', array('get_parent_child_category_ids'));
+
+    $dbi->expects($this->any())
+        ->method('get_parent_child_category_ids')
+        ->will($this->returnValue(array(1 => 0, 2 => 1, 3 => 2, 4 => 2, 5 => 0)));
+
+    $css->expects($this->any())->method('get_comicpress_dbi')->will($this->returnValue($dbi));
 
 		$this->assertEquals(array(
 			'0' => array(
@@ -298,7 +302,7 @@ class ComicPressStorylineTest extends PHPUnit_Framework_TestCase {
 					)
 				)
 			)
-		), $this->css->get_category_simple_structure(1));
+		), $css->get_category_simple_structure(1));
 
     $this->assertEquals(array(
       '0' => array(
@@ -310,7 +314,7 @@ class ComicPressStorylineTest extends PHPUnit_Framework_TestCase {
         ),
         '5' => true
       )
-    ), $this->css->get_category_simple_structure());
+    ), $css->get_category_simple_structure());
 	}
 
 	function providerTestNormalizeFlattenedStoryline() {