Kearnen doesn't like your plan. Unfortunately, she turns out to be right when you discover upon arriving at Sentinel Hill that your detour to Mortwake has given the Defias kingpin enough time to burn Sentinel Hill and leave for Moonbrook. Having already trusted the goblin this far, you trust him far enough to help Kearnen trail the kingpin, but his plan falls through too when you discover Mortwake also there with a zombie army. A three-way melee breaks out, in which you barely manage to escape with your lives by setting your tank to self-destruct.
At least the Defias is gone too.