Burnt wire in trunk of 88 'Bird

While installing new speakers in my trunk, I found a burnt red wire. It is located on the passenger side. Everything was working fine last time I drove it a couple days ago. Car has premium sound system w/Infinity after market speakers. Everything still works. The only thing I can find wrong is that the power switch on the EQ has given up but if you hold it EQ comes on. I had it repaired several years ago and never switched it off. Any ideas what this is for? I can repair and add a fuse but would still like to know what is for.
http://natomessageboard.com/uploads/0000...dtrunk.jpg
http://natomessageboard.com/uploads/0000...trunk2.jpg

Where does it run to in the trunk?