S1 episode 1
Elliot is a young programmer in New York City who works as a cyber-security engineer by day and as a vigilante hacker by night. He's a loner and occasional drug user with a social phobia of being around most people. He believes in using his computing talents to help those he cares about, as well as to punish those he believes are bringing harm to others.
Elliot discovers that the owner of a coffee shop he frequents is hiding a terrible criminal secret. Uncharacteristically confronting the owner in person, Elliot tells him how he uncovered the information, and then leaves just as the police arrive. Elliot also hacks his best friend Angela to keep watch over her, and his psychologist to protect her from unscrupulous suitors.
At his day job at a cyber-security firm, Elliot thwarts a hack on their biggest client, but in the process discovers some secret lines of code meant for his eyes only. He chooses to leave the code in place, curious to see the meaning of it.
On his way home on the subway, Elliot is approached by man with a "Mr. Robot" patch on his jacket. The stranger appears to be a down-on-his-luck drifter, but Elliot has seen him before and surmises that he's been following Elliot. The stranger confirms that Elliot left the secret code in place, and then leads him to Coney Island. Once there, Elliot is introduced to a secret team of hackers who are determined to bring their version of justice to the world.
Elliot must now choose -- he can either continue as a lone vigilante, or risk both his anonymity and potential freedom by joining this mysterious group. They seem to be as talented and driven as he is – but as Elliot soon learns, entry may come with a cost.