Duster felt the tension grow between Mary and the Doctor as their conversation continued, and he had backed further away from the two, towards the portal. He wasn't the sort of person to handle heated debates, which he feared this would turn into.

The Doctor was an important figure in Jack's world. Someone busy. He surely wouldn't have the time to work on everything. But at the same time, there was a feeling that he didn't much like Mary's work. Both were right. Duster wouldn't be able to pick a side if it came down to him.

He turned away just as Mary threw her fist. The swift action caught his attention, and Duster rushed to the scene, stopping several feet away in case he needed to interfere in a fight.