Footer content plugin has broken my site - help!

Hi, I'm a newbie to WPMU and have mistakenly installed and activated the footer content plugin on a new WP single site I'm developing, not spotting first that it is for WP Multisite only. My bad!
But now I can't do anything with the site - the words "The Footer Content plugin is only compatible with WordPress Multisite." come up every time I try to do anything, even if I try to log back into the site again. Screenshot attached.
Presumably, the thing to do is delete the plugin at source, but I'm hosted by Dreamhost, which has been down for about an hour.