Listen, Naomi Watts puts on an incredible performance as Nora Brannock, but Bobby Cannavale practically steals the entire show in his portrayal of her husband, Dean, a man more concerned with outward appearances of perfection and wealth than his family's own safety and happiness. The pair also have two children, Ellie (Isabel Gravitt) and Carter (Luke David Blumm), who quickly become intermixed in the drama, as well.
We witness the downward transition of Dean's mental state as he becomes more and more entranced with the house and the person behind the threatening letters that just won't stop coming to his mailbox. But the conflict isn't just confined to the house itself.
Margo Martindale and Richard Kind play Maureen and Mitch, a married couple who lives just across the way from the Brannocks. Always donning matching outfits and unapologetically sitting in their lounge chairs with binoculars to spy on their new neighbors, it's no surprise that the pair is at the top of Dean's list of who could potentially be The Watcher.
Terry Kinney and Mia Farrow are the brother-sister duo of Jasper and Pearl Winslow, who also live extremely close to the Brannock's home. Pearl is her brother's mysterious mouthpiece, as Jasper is voluntarily mute and quickly makes his way to the top of Dean's list of potential Watchers as he's obsessed with 657 Boulevard.
Then, of course, we've got Karen Calhoun (Jennifer Coolidge), the odd realtor who's desperate to relist the Brannock's home after they start receiving the letters. For that reason alone, her true intentions become a little suspicious as she's beyond eager to get the Brannocks out of their new house.
Once the letters began, Dean hired Dakota (Henry Hunter Hall), a 19-year-old who runs his own security business and installs alarms and cameras all over the Brannock's home. But when other evidence comes to light, Dean moves Dakota to the top of his Watcher list, especially since he suspects that his daughter, Ellie, has struck up an intimate relationship with him.
In Dean's current mental state, practically anyone could be The Watcher.