If you're purling on the way back, then the yarn would be carried along the front (which, on the purl side, would be the wrong side facing you).
If you're knitting on the way back, then you'll have to bring the carried yarn to the front and then bring the yarn in use to the back and knit the next stitch(es). Then you'd bring that to the front and the next yarn to the back.
Does that answer your question?
Do you have a link/picture to/of the pattern?