Unroll the leaf and see if there's a caterpillar in there. He might be the culprit who chewed through the other. The brown shriveled one does sound like some kind of fungal disease. I'd get rid of it fast before it attacks the rest. Discard the soil too and if you are going to use the pot again sterilize it with bleach

Thanks, Dave. The only picture I was able to find that looked like what's on my plant is what I saw on this blog: http://inadvertentgardener.wordpress.com/2006/08/18/basil-to-scale/ The blog stated it was scale but a search on gardenweb described it as being oedema/edema, as it did not pass one poster's try-and-scratch-it-off-with-your-fingernail test. My search for edema resulted in mostly medicinal uses and with the exception of the aforementioned blog, I have yet to find another picture resembling my plant. You're right, the plant is going to be toast shortly (forecast for upper thirties over the weekend) but since it is in a container I was hoping to extend the harvest by moving it indoors on cold nights. My main concern is that it will not be harmful to anyone who consumes the plant's leaves. Oh, almost forgot - It's a Genovese Basil plant. Thanks again! Lisa

If there are no other symptoms, then it could be grey mould (Botrytis). However, it also looks like there might be some faint yellowing patches...? It'd be more visible on the topside of the leaf. If so then it might be downy mildew (Peronospora). Have a look at some images of the two online and compare.

check the back for aphids ... or other insects since presumably you eat these... it might be cheaper.. and easier.. to secure some new CLEAN plants ... rather than spending a lot of time and some money on remedy ... and if you plan on taking them indoors... make sure there are no bugs by that time ...especially if you have other houseplants ... where are you .. tell us each time.. i will guess.. GB means britian??? ken