When No One Is Watching introduces Brooklyn native Sydney Green, who is tired of seeing the neighbourhood she loves being constantly changed. New buildings are popping up, her beloved neighbours are moving away, and there's a For Sale sign everywhere she looks. As an attempt to grasp onto what is left of her treasured community, she attends a walking tour and finds an unlikely ally in her neighbour, Theo. When Sydney and Theo begin researching the history of their stomping grounds, they discover the changes being made might be more sinister than they though.