Script for killing an npc and advancing to next stage NOT working

[RiotMan117]

I'm going to make this nice and simple. I write a script for an npc:

scn MarcusHuntedDown

Begin OnDeath

If Getstage ThinningTheHerd ==10
   SetStage ThinningTheHerd 20 
Endif

END
 

and it does nothing. When the NPC is killed the marker goes away but the quest does not advance to the next stage. The quest still tells you to kill this npc. Thanks.