@Capt_Gigglepants:
Not sure about that.
My guess would be that a curse that is "dispelled" by the magic / skill Douglas used is not actually dispelled but removed from the original victim and sent back to caster.
If that is the case then the curse would have returned to Alan and would now work on him.
The other possibility would be that (like in many settings) spells (including curses) are connected to their casters as long as they are active.
In the case that a spell or a curse is interupted or dispelled that connection will cause a negative feedback to fall onto the caster that is equivalent to the original spell's / curse's power.
Therefore in this case the curse being cancelled by Douglas would have caused an equally destructive feedback onto Alan as a result.