function overloading in Javascript

I need base functionality for a character, then extend a handful of the base functions for customizing certain characters. I'm trying to use classes and inheritance, but not getting something right. Here's relevant code:

SwapCharacter.js

 #pragma strict
 class SwapCharacter extends MonoBehaviour {
 
 var TakeOverLight:GameObject;
  
 virtual function Start()     
 {
 TakeOverLight=GameObject.Find("TakeOverLight");

 TakeOverLight.active=false;
 }  
 }  

**SwapCharacterExtended.js**

 #pragma strict
 
 class SwapCharacterExtended extends SwapCharacter{

 }

`

This throws a NullReference on TakeOverLight.Active in Start(). It seems to me that Start is somehow called twice. The first instance kills the light, then on the second path, it's inactive and can't be found. Am I overloading the function properly? It runs fine if I delete the SwapCharacterExtends.js...