You will need this plugin in case your site becomes broken due to a child theme (mis)configuration.
If your site is totally broken you may have to download the file and then upload the plugin's file directly into wp-content/mu-plugins/ that way it will be run before other plugins.
Free Download from http://wordpress.org/plugins/orbisius-theme-fixer/
Scenario #1 : Your site is totally broken
Did you NOT hear about our cool service called qsandbox.com?
Unzip the file on your computer and then using an FTP program upload just orbisius-theme-fixer.php in wp-content/mu-plugins.
If that mu-plugins folder doesn’t exist create it.
Next, login as you would normally log into WordPress admin.
Then go to Appearance > themes. One of the default WordPress themes should be active (that’s what the theme fix plugin did).
Now, you need to activate the parent theme that you used or any theme are you know worked.
The page will refresh but it will still showing one of the default WordPress themes.
Now you can remove theorbisius-theme-fixer.php file from /wp-content/mu-plugins/
Scenario #2 : Your site is partially broken
Upload the ZIP file that you just downloaded as you normally would with WordPress plugins (Admin > Plugins > Add > Upload).
Then go to Appearance > themes. Activate a theme that worked before.
Deactivate Orbisius Theme Fixer so the selected theme is used.
No direct database changes are made by this plugin.