With Zahrah gone, Quinn just wanted to solve this mystery and find out why Walter betrayed the woman he loved like that.
Although he killed her in the end, he wasn't a fool to not see that Walter loved Zahrah so much. There should be a reason why it ended that way, right?
As if the person behind all this drama heard his prayer, suddenly he found himself watching Walter again.
And when he saw the other, Quinn no longer had any strength to say anything or even defend the traitor.
Walter was working for the dark faction, the bad guys and his job from the beginning was to seduce the saintess, confuse her heart and, when she was muddleheaded, kill her and give a huge blow towards the light faction.
Being raised by the dark faction from a young age, Walter had followed the organization's orders to the t, without question.