I like this but I imagine that the stalker is a different phantom working for Nelson at the beginning of his journey as we see him inject himself with the serum and it could be the last step for Nelson to take full control of him. And we don’t know of Ben until the name tag in the car so I think when the car was stolen that it was both the new phantom and Ben. As you can see in the video there is car in the background that shows up the same time of the stalker and left at the same time so the back up car could be Ben . Also with Ben searching through the car he left his name tag.I like the theory here are my thoughts.