help with color in shader

Hi
Sorry I'm a newbie with shaders. I got this shader (forgot where from) and I try to change the rim color to black. If I do thiswith the shader controls, the figure becomes 100% transparent. I want to keep the rim visible, as in the img attached, but in black. Any ideas?

Code (CSharp):

1. Shader "Custom/Model_TransparentInvert" {
2.      Properties
3.      {
4.        _InnerColor ("Inner Color", Color) = (0.0, 0.0, 0.0, 1.0)
5.        _RimColor ("Rim Color", Color) = (1.0,1.0,1.0,1.0)
6.        _RimPower ("Rim Power", Range(0.5,8.0)) = 2.47
7.      }
8.      SubShader
9.      {
10.        Tags { "Queue" = "Transparent" }
11.      
12.        Cull Back
13.        Blend One One
14.      
15.        CGPROGRAM
16.        #pragma surface surf Lambert
17.      
18.        struct Input
19.        {
20.            float3 viewDir;
21.        };
22.      
23.        float4 _InnerColor;
24.        float4 _RimColor;
25.        float _RimPower;
26.      
27.        void surf (Input IN, inout SurfaceOutput o)
28.        {
29.            o.Albedo = _InnerColor.rgb;
30.            half rim = 1.0 - saturate(dot (normalize(IN.viewDir), o.Normal));
31.            o.Emission = _RimColor.rgb * pow (rim, _RimPower);
32.        }
33.        ENDCG
34.      }
35.      Fallback "Diffuse"
36.    }
37.