Can't make material Transparent?

I’m doing an outline effect in blender cycles using a displacement modifier, duplicate mesh, and the backface option on a geometry node.

Here is a picture of my set up: enter image description here

The displaced duplicate mesh is placed directly on top of the original mesh. The original mesh has a red transparent shader, but isn’t transparent at all.

How do I get it so that internal mesh becomes transparent? Any advice would be appreciated, thank you.

It’s not very clear: what is the material in the nodetree for? The big red monkey in foreground? so where is that red color coming from? and anyway, for a closed object using backface will not give you the outline
blend file?