A young photographer insinuates himself into the entourage surrounding an up-and-coming pop singer. On social media, a lurker is someone who mostly just reads other people’s posts but, for whatever reason, rarely participates. In the recent film Lurker, written and directed by Alex Russell, this idea is combined with that of the fan or follower, someone devoted to or obsessed with a celebrity. The result is a different kind of suspense, exploring the psychology of someone on the margins desperate to stand in the light of someone else’s fame. Matthew Morning is a shy gawky young man working at a…