in the engineering room
Jack left the Doctor in 202. Rose having left before off to go claim a room of her own. Jack was headed down to find Harper to return the gun he borrowed when he'd gone out to find Rose. So after Harper not being in 202 with them at the time of their discussion, the most logical place to find him would be in the machine shop.
Jack hadn't ventured down there more than once, he could see that now changing.
"Hello? Harper?" He called as he wandered past the work benches and other furniture that made up the room.
Jack hadn't ventured down there more than once, he could see that now changing.
"Hello? Harper?" He called as he wandered past the work benches and other furniture that made up the room.