"Does that mean it's working?" 

He really doesn't have to move again, of he wants. He can stay here; nobody will miss him at home. Might as well just stay in this spot forever. 

He might as well, especially with the branches threading through and over his limbs and torso and face.

As the branches completely cover Josh's body, they begin to thicken and merge with each other, forming a single trunk. Some branches twist away while the top rises, splitting and growing little black leaves. The bark of the trunk stretches as the tree grows, until bits of it tear and reveal dark sap and wood, in a shape a bit like Josh's face.

"It is done. He will be preserved."

"...Okay. Can I talk to him? I guess trees don't work like that..." 

"You can talk to him. He will hear and understand you, but very slowly."

"Okay. Can we be alone?" 

The arborist nods, and the two lights in the shadows disappear.

"Josh? How are you feeling buddy? You're looking a bit stiff." 

The tree remains silent and still.

"Right. You're a tree. I hope that's okay. I should get going."

He awkwardly pets the tree.

The tree's bark is fairly smooth. It gets a little bit of black oily sap on his hand.

Right. Time to report back.

"I should go."

He turns to face the other trees.

"You can come back now," he shouts.

Two lights become visible in the shadows of some far-away trees, moving closer and occasionally passing behind trees and becoming visible again much closer.

When the arborist is near the trees he was by earlier, he stops and asks "Is there anything else you wish to test?"

"I think I've had enough testing for one day. Is there anything else you or our Supreme Leader wanted to get done?"

"Testing whether your world's witches could travel here, and whether vampires could be preserved, was all that we planned for this trip."

"Guess we've done both, then. It was nice meeting you."

And it's time for the witch to travel back, and for the vampire to enjoy being preserved.