diff --git a/inc/activities.php b/inc/activities.php
new file mode 100644
index 0000000..c0a7748
--- /dev/null
+++ b/inc/activities.php
@@ -0,0 +1,43 @@
+<?php
+namespace activities;
+
+function get_activity( $id ) {
+    global $wpdb;
+    $activity_json = $wpdb->get_var( sprintf(
+        'SELECT activity FROM activitypub_activities WHERE id = %d', $id
+    ) );
+    if ( is_null( $activity_json ) ) {
+        return new \WP_Error(
+            'not_found', __( 'Activity not found', 'activitypub' ), array( 'status' => 404 )
+        );
+    }
+    $activity = json_decode( $activity_json );
+    $activity['id'] = get_activity_url( $id );
+    return $activity;
+}
+
+function persist_activity( $activity ) {
+    global $wpdb;
+    $wpdb->insert(
+        'activitypub_activities', array( 'activity' => wp_json_encode( $activity ) )
+    );
+    $activity["id"] = get_activity_url( $wpdb->insert_id );
+    return $activity;
+}
+
+function get_activity_url( $id ) {
+    return get_rest_url( null, sprintf( '/activitypub/v1/activity/%d', $id ) );
+}
+
+function create_activities_table() {
+    global $wpdb;
+    $wpdb->query(
+        "
+        CREATE TABLE IF NOT EXISTS activitypub_activities (
+            id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+            activity TEXT NOT NULL
+        );
+        "
+    );
+}
+?>
diff --git a/inc/init.php b/inc/init.php
index afc8598..dcabbb9 100644
--- a/inc/init.php
+++ b/inc/init.php
@@ -4,13 +4,15 @@ namespace init;
 require_once plugin_dir_path( __FILE__ ) . '/outbox.php';
 require_once plugin_dir_path( __FILE__ ) . '/api.php';
 require_once plugin_dir_path( __FILE__ ) . '/objects.php';
+require_once plugin_dir_path( __FILE__ ) . '/activities.php';
 
 add_action( 'rest_api_init', function() {
     \api\register_routes();
 } );
 
 add_action( 'activitypub_init', function() {
-    \outbox\create_outbox_table();
+    \activities\create_activities_table();
     \objects\create_object_table();
+    \outbox\create_outbox_table();
 } );
 ?>
diff --git a/inc/objects.php b/inc/objects.php
index 4bdcdd1..40a5a1b 100644
--- a/inc/objects.php
+++ b/inc/objects.php
@@ -4,21 +4,27 @@ namespace objects;
 function persist_object( $object ) {
     global $wpdb;
     $wpdb->insert( 'activitypub_objects', array( 'object' => wp_json_encode( $object ) ) );
-    $object["id"] = get_object_url( $wpdb->insert_id );
+    $object['id'] = get_object_url( $wpdb->insert_id );
     return $object;
 }
 
 function get_object( $id ) {
     global $wpdb;
-    $object = json_decode( $wpdb->get_var( sprintf(
+    $object_json = $wpdb->get_var( sprintf(
         'SELECT object FROM activitypub_objects WHERE id = %d', $id
-    ) ) );
-    $object["id"] = get_object_url( $id );
+    ) ); 
+    if ( is_null( $object_json ) ) {
+        return new \WP_Error(
+            404, __( 'Object not found', 'activitypub' ), array ( 'status' => 404 )
+        );
+    }
+    $object = json_decode( $object_json );
+    $object['id'] = get_object_url( $id );
     return $object;
 }
 
 function get_object_url( $id ) {
-    return get_rest_url( null, sprintf( '/activitypub/v1/object/%d', $id );
+    return get_rest_url( null, sprintf( '/activitypub/v1/object/%d', $id ) );
 }
 
 function create_object_table() {
diff --git a/inc/outbox.php b/inc/outbox.php
index 4513ed3..3fea279 100644
--- a/inc/outbox.php
+++ b/inc/outbox.php
@@ -13,34 +13,35 @@ When an Activity is received (i.e. POSTed) to an Actor's outbox, the server must
 namespace outbox;
 
 require_once plugin_dir_path( __FILE__ ) . '/activities/create.php';
+require_once plugin_dir_path( __FILE__ ) . '/activities.php';
 
 function handle_activity( $actor, $activity ) {
     if ( !array_key_exists( "type", $activity ) ) {
-        return new WP_Error(
+        return new \WP_Error(
             'invalid_activity',
             __( 'Invalid activity', 'activitypub' ),
             array( 'status' => 400 )
         );
     }
-    switch ( $activity["type"] ) {
-    case "Create":
+    switch ( $activity['type'] ) {
+    case 'Create':
         $activity = \activites\create\handle( $actor, $activity );
         break;
-    case "Update":
+    case 'Update':
         break;
-    case "Delete":
+    case 'Delete':
         break;
-    case "Follow":
+    case 'Follow':
         break;
-    case "Add":
+    case 'Add':
         break;
-    case "Remove":
+    case 'Remove':
         break;
-    case "Like":
+    case 'Like':
         break;
-    case "Block":
+    case 'Block':
         break;
-    case "Undo":
+    case 'Undo':
         break;
     default:
         // handle wrapping object in Create activity
@@ -60,16 +61,16 @@ function deliver_activity( $activity ) {
 
 function persist_activity( $actor, $activity ) {
     global $wpdb;
-    $activity_json = wp_json_encode( $activity );
+    $activity = \activities\persist_activity( $activity );
+    $activity_id = $wpdb->insert_id;
     $wpdb->insert( 'activitypub_outbox',
                    array(
-                       "actor" => $actor,
-                       "activity" => $activity_json,
+                       'actor' => $actor,
+                       'activity_id' => $activity_id,
                    ) );
-    // TODO hydrate $activity["id"] with URL to activity using $wpdb->insert_id
-    $response = new WP_REST_Response( $activity );
+    $response = new WP_REST_Response();
     $response->set_status( 201 );
-    // TODO set location header of response to created activity URL
+    $response->header( 'Location', $activity['id'] );
     return $response;
 }
 
@@ -80,7 +81,7 @@ function create_outbox_table() {
         CREATE TABLE IF NOT EXISTS activitypub_outbox (
             id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
             actor VARCHAR(128) NOT NULL,
-            activity TEXT NOT NULL
+            activity_id INT UNSIGNED FOREIGN KEY REFERENCES activitypub_activities(id)
         );
         "
     );