She's watching you, but who's watching her? Lily Gullick lives with her husband, Aiden, in a brand-new apartment opposite a building that has been marked for demolition. A keen bird-watcher, she can't help spying on her neighbors. Until one day Lily sees something suspicious through her binoculars, and soon her elderly neighbor Jean is found dead. Convinced of foul play, she knows she has to act. But her interference is not going unnoticed, and as she starts to get close to the truth, her own life comes under threat. But can Lily really trust everything she sees?