mammoth launch of “Dahmer,” “The Watcher” adaptation drains all the potential relatability and genuine terror out of the source material. With a subtler hand, and a much shorter runtime, a film could have explored the rich themes of the dark side of upward mobility and the erosion of civility among neighbors while serving up subtle but real scares, toying with the idea that the titular letter-writer could be any smiling neighbor at the grocery store.The neighbors in Murphy’s “The Watcher” wouldn’t be even remotely recognizable in the real world, so we get none of that all-too-believable dread.