Simon James, portrayed by Jesse Eisenberg, is a young Canadian man navigating life in London. His journey begins with a frustrating incident on the tube, where he finds himself losing his briefcase after the handle breaks, leaving him without his ID badge at work. This small mishap leads him to confront multiple challenges throughout his day, including pitching ideas to his boss, Wallace Shawn, and learning that he will be tutoring his boss’s daughter, Melanie, played by Yasmin Paige.
During a visit to his mother in a nursing home, he meets an elderly resident who hints that something about Simon is "not right." Back at his apartment, Simon becomes infatuated with his co-worker, Hannah, brought to life by Mia Wasikowska. His fascination grows to an unsettling level as he sets up a telescope to observe her from across the street. However, an alarming event occurs when Simon witnesses a man jump to his death from a building, learning that if the man had landed differently, he could have survived.
As Simon and Hannah’s relationship begins to blossom, he becomes more desperate to connect. He takes her out to dinner but is abruptly distracted by a call from his mother. Upon returning, he finds a note from Hannah suggesting that she will see him again, which leads him to trade in his television to buy her a gift. His life takes a surreal twist when he encounters a doppelgänger, another Simon named James, also played by Jesse Eisenberg. This identical stranger causes chaos, leading to an intertwining of their lives, as James quickly gains popularity at work and even catches Hannah's eye.
As James begins to overshadow Simon, tensions rise when Simon pretends to be James on a date with Hannah, with James feeding him lines through an earpiece. This charade further complicates their relationships, leading to heartbreak as James kisses Hannah, leaving Simon feeling more invisible than ever. Things escalate when James blackmails Simon into handing over the key to his apartment, manipulating their friendship for his own gain.
The culmination of Simon's emotional turmoil peaks when he confronts James, leading to a confrontation where Simon's hidden feelings and frustrations explode, resulting in him being fired from his job. In a dark moment, he contemplates suicide, only to be pulled back by disturbing news about Hannah, who finds herself in a precarious situation following her emotional distress over James.
After a series of tragic events—including the death of his mother and the ensuing chaos at her funeral—Simon discovers the depth of his connection to James and their intertwined fates. In a desperate bid for attention and recognition, he plans a dramatic gesture, handcuffing James and attempting to leap from a building. In a moment of self-determination, Simon jumps, landing on an awning and sustaining severe injuries.
As an ambulance arrives and he finds solace in Hannah’s presence, Simon reflects on his unique identity, stating, > "I'd like to think I'm pretty unique." In this tale of identity, desperation, and the quest for visibility, Simon’s journey ultimately reveals the complex interplay of human relationships and self-worth.
