diff --git a/src/Discovery/PathFinderBase.php b/src/Discovery/PathFinderBase.php
index 41ece1c..7f2bd6f 100644
--- a/src/Discovery/PathFinderBase.php
+++ b/src/Discovery/PathFinderBase.php
@@ -8,7 +8,7 @@
 namespace Drupal\Composer\ClassLoader\Discovery;
 
 
-class PathFinderBase implements PathFinderInterface {
+abstract class PathFinderBase implements PathFinderInterface {
 
   /**
    * The relative path.
@@ -27,4 +27,12 @@ public function __construct($path) {
     $this->path = $path;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function requireFile($seed) {
+    $real_path = $this->find($seed);
+    require_once $real_path;
+  }
+
 }
diff --git a/src/Discovery/PathFinderContrib.php b/src/Discovery/PathFinderContrib.php
index cdd6f54..37ecf4a 100644
--- a/src/Discovery/PathFinderContrib.php
+++ b/src/Discovery/PathFinderContrib.php
@@ -8,6 +8,66 @@
 namespace Drupal\Composer\ClassLoader\Discovery;
 
 
+use Drupal\Composer\ClassLoader\ClassLoaderException;
+
 class PathFinderContrib extends PathFinderBase implements PathFinderInterface {
 
+  /**
+   * The module name.
+   *
+   * @var string
+   */
+  protected $moduleName;
+
+  /**
+   * Constructs a PathFinderContrib object.
+   *
+   * @param string $path
+   *   The relative path to find.
+   * @param string $module_name
+   *   The name of the contrib module to find.
+   */
+  public function __construct($path, $module_name) {
+    $this->path = $path;
+    $this->moduleName = $module_name;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function find($seed) {
+    $core_finder = new PathFinderCore('');
+    if (!$core_path = $core_finder->find($seed)) {
+      return NULL;
+    }
+    $core_directory = new \RecursiveDirectoryIterator($core_path . '/sites', \FilesystemIterator::KEY_AS_PATHNAME | \FilesystemIterator::CURRENT_AS_FILEINFO | \FilesystemIterator::SKIP_DOTS);
+    $files_iterator = new \RecursiveIteratorIterator($core_directory, \RecursiveIteratorIterator::SELF_FIRST);
+    // Iterate over all of the directories under the sites directory.
+    foreach ($files_iterator as $path_name => $dir) {
+      /** @var $dir \SplFileInfo */
+      if (!$dir->isDir()) {
+        continue;
+      }
+      // Check if the current directory corresponds to the contrib we are
+      // looking for.
+      if ($this->isWantedContrib($dir)) {
+        return $dir->getPathname() . '/' . $this->path;
+      }
+    }
+    throw new ClassLoaderException(sprintf('Drupal module "%s" could not be found in the Drupal tree that contains: %s.', $this->moduleName, $seed));
+  }
+
+  /**
+   * Checks if the passed directory is the contrib module we are looking for.
+   *
+   * @param \SplFileInfo $dir
+   *   The info object about the directory.
+   * @return bool
+   *   TRUE if the contrib is detected. FALSE otherwise.
+   */
+  protected function isWantedContrib(\SplFileInfo $dir) {
+    $info_file = $dir->getPathname() . '/' . $this->moduleName . '.info';
+    return file_exists($info_file);
+  }
+
 }
diff --git a/src/Discovery/PathFinderCore.php b/src/Discovery/PathFinderCore.php
index 4f9c78f..2a353c8 100644
--- a/src/Discovery/PathFinderCore.php
+++ b/src/Discovery/PathFinderCore.php
@@ -7,7 +7,73 @@
 
 namespace Drupal\Composer\ClassLoader\Discovery;
 
+use Drupal\Composer\ClassLoader\ClassLoaderException;
 
 class PathFinderCore extends PathFinderBase implements PathFinderInterface {
 
+  /**
+   * {@inheritdoc}
+   */
+  public function find($seed) {
+    $seed = realpath($seed);
+    // Try to create the iterator with the seed.
+    try {
+      $directory = new \DirectoryIterator($seed);
+    }
+    catch (\UnexpectedValueException $e) {
+      // If the seed was not a directory, then get the parent directory.
+      $path_info = pathinfo($seed);
+      $directory = new \DirectoryIterator($path_info['dirname']);
+    }
+    do {
+      if ($this->isDrupalRoot($directory)) {
+        return $directory . '/' . $this->path;
+      }
+    }
+    while ($directory = $this->getParentDirectory($directory));
+    throw new ClassLoaderException(sprintf('Drupal core directory could not be found as a parent of: %s.', $seed));
+  }
+
+  /**
+   * Checks if the passed directory is the Drupal root.
+   *
+   * @param \DirectoryIterator $directory
+   *   The directory iterator item.
+   *
+   * @return bool
+   *   TRUE if the passed directory is the Drupal root.
+   */
+  protected function isDrupalRoot(\DirectoryIterator $directory) {
+    // Check if there is a COPYRIGHT.txt file in the directory.
+    foreach ($directory as $item) {
+      if (!$item->isFile() && $item->getFilename() != 'COPYRIGHT.txt') {
+        continue;
+      }
+      $line = fgets(fopen($item->getPathname(), 'r'));
+      return strpos($line, 'All Drupal code is Copyright') === 0;
+    }
+    return FALSE;
+  }
+
+  /**
+   * Gets the parent directory iterator.
+   *
+   * @param \DirectoryIterator $directory
+   *   The current directory iterator.
+   *
+   * @return \DirectoryIterator
+   *   The parent directory.
+   */
+  protected function getParentDirectory(\DirectoryIterator $directory) {
+    $path_name = $directory->getPathname();
+    $path_info = pathinfo($path_name);
+    if (!empty($path_info['dirname'])) {
+      try {
+        return new \DirectoryIterator($path_info['dirname']);
+      }
+      catch (\UnexpectedValueException $e) {}
+    }
+    return NULL;
+  }
+
 }
diff --git a/src/Discovery/PathFinderInterface.php b/src/Discovery/PathFinderInterface.php
index 4a871af..382b2f1 100644
--- a/src/Discovery/PathFinderInterface.php
+++ b/src/Discovery/PathFinderInterface.php
@@ -10,4 +10,27 @@
 
 interface PathFinderInterface {
 
+  /**
+   * Finds and requires the current file.
+   *
+   * @throws \Drupal\Composer\ClassLoader\ClassLoaderException
+   *   If the file could not be found.
+   */
+  public function requireFile($seed);
+
+  /**
+   * Finds the current file in the file system.
+   *
+   * @param string $seed
+   *   A path where to start looking for. Typically it will be the composer.json
+   *   file name that contains the configuration.
+   *
+   * @throws \Drupal\Composer\ClassLoader\ClassLoaderException
+   *   If the file could not be found.
+   *
+   * @return string
+   *   The name of the real path. NULL if the file was not found.
+   */
+  public function find($seed);
+
 }
diff --git a/src/Discovery/PathFinderNull.php b/src/Discovery/PathFinderNull.php
index 00d39c6..f7af936 100644
--- a/src/Discovery/PathFinderNull.php
+++ b/src/Discovery/PathFinderNull.php
@@ -12,9 +12,8 @@ class PathFinderNull extends PathFinderBase implements PathFinderInterface {
   /**
    * {@inheritdoc}
    */
-  public function requireFile() {
-    require_once $this->path;
-    return TRUE;
+  public function find($seed) {
+    return $this->path;
   }
 
 }
diff --git a/src/Loader.php b/src/Loader.php
index cbf372a..ad18530 100644
--- a/src/Loader.php
+++ b/src/Loader.php
@@ -27,11 +27,17 @@ public static function autoload($class) {
     if (!in_array($class, static::$classMap)) {
       return FALSE;
     }
-    $resolver = new TokenResolver(static::$classMap[$class]);
-    $finder = $resolver->resolve();
-    // Have the path finder require the file and return TRUE or FALSE if it
-    // found the file or not.
-    return $finder->require();
+    try {
+      $resolver = new TokenResolver(static::$classMap[$class]);
+      $finder = $resolver->resolve();
+      // Have the path finder require the file and return TRUE or FALSE if it
+      // found the file or not.
+      $finder->requireFile();
+      return TRUE;
+    }
+    catch (ClassLoaderException $e) {
+      return FALSE;
+    }
   }
 
   /**