Question
I have brought my pepper plants inside again this year but on some of the leaves there are black bits on the underside and I also found a clear worm/catipillar with a dark head.

What is this beastie and is the soap and water trick the best way to get rid of them?

Answer
Guy,

Post a picture if you can because there are many things that fit this general description. The "black bits" are probably frass from the caterpillar. Insecticidal soap is a good option but neem oil might be better if they are still feeding. Here's an article about neem oil insecticide http://www.livingwithbugs.com/neem_oil.html if you are not familiar with this material.

Jack DeAngelis
http://www.livingwithbugs.com