HOWTO recover after bad plugin activation

I get a server error every way I try to access my blog.
My site is hosted and was working before I killed it.

I installed and activated a plugin. All looked fine. When I tried the main page, I get the error. Same error when I try the admin page.

I tried to find the folder(s) for the failing plugin but I cannot locate anything with a reasonable name. I was going to delete that folder tree and see what I get after that. I don’t know what else to do.

Thanks in advance,
~~~ 0;-Dan