Billionaire playboy Oliver Queen, CEO of Queen Industries, returns to Star City after three years stranded on an island in the Pacific Ocean after falling from his yatch during a storm. Changed by his experiences on the island, Oliver and his friend, Queen Industries' attorney Will Hackett, create an arsenal of weapons that Oliver uses to adopt the identity of an urban crimefighter called Green Arrow.
During a beneficent party, Oliver and Hackett are confronted by Oliver's business rival, David Cross, CEO of Cross Enterprises. Meanwhile, professional assassin Arthur Merlyn invades the headquarters of Checkmate, a secret governmental agency created to monitor metahuman activity on Earth, and murders director Colonel Taleb Beni Khalid with copies of Green Arrow's trick arrows.
Oliver hears of a break-in at Checkmate's headquarters and changes into Green Arrow, arriving there only to learn he has been framed for Khalid's murder. The police arrives and eventually captures him. His secret identity is exposed to the public and he is sentenced to life imprisionment at the SuperMax Penitentiary for Metahuman Criminals, run by warden Amanda Waller.
Arriving at the SuperMax, Oliver learns that the inmates are divided in three categories: The Green Suits (average humans with advanced weaponry), the Blue Suits (genius-level humans) and the Orange Suits (superpowered metahumans). The Orange Suits are implanted with the Parallax Device, a microchip that causes pain if they use their powers for more than one minute.
Oliver is designated a Green Suit and befriends Split, a teleporter who explains to him that the SuperMax's layout changes every night to avoid breakout attempts. Waller, an old friend of Khalid, begins to torture Oliver as revenge for Khalid's murder, and punishes him with solitary confinement after he gets into a fight with the Aryan Nation, a trio of superpowered supremacists formed by Iron Cross, Hatemonger and Blacklash.
In solitary, Oliver meets Hartley Rathaway, the Pied Piper, who can control other people through sonic vibration. Rathaway has found a frequency that allows him to use his powers without being detected by the Parallax Device, and together, Oliver and Rathaway decide to escape.
Meanwhile, Cross meets with Hackett, who helped him frame Green Arrow of Khalid's murder so Cross could take over Queen Industries and Hackett could steal Oliver's fortune. They learn that a legal loophole requires that Oliver is dead in order for their plan to continue, so Cross infiltrates Merlyn in the SuperMax with orders to eliminate Oliver.
Oliver and Rathaway deduce that the SuperMax is located in the Pacific Ocean and are forced to enlist the help of other inmates in order to escape: Cameron Mahkent, the Icicle, who can manipulate ice; Gemini De Mille, who can shapeshift; Cascade, who can manipulate water; and Split.
Together, they create a tunnel that'll lead them to freedom. Oliver then arranges for another inmate, Abel Tarrant, the Tattooed Man, to make a Flash Drive for them. He uses it to contain Djinn, a living computer virus, and then gets into a fight with Albert Desmond, the Blockbuster, "king" of the Orange Suits. Reassigned to clean-up duty, Oliver takes the opportunity to upload Djinn into the SuperMax's grid.
Djinn disables the Parallax Devices, leading to a riot. Oliver and his group use this opportunity to escape. Oliver is attacked by Merlyn, who was provided with his weapons by a corrupt security guard, but manages to evade him, and Merlyn is captured by Waller's forces. Blockbuster also learns of their plans and murders Split to take his place in the team.
Oliver, Rathaway, Mahkent, Gemini and Cascade are forced to accept Blockbuster in the team, and they go through the tunnel only to learn that the sky above the SuperMax is a holographic projection, and the prison is actually located in the Artic.
Cascade is murdered by Waller's men, but the other manage to escape and hide in a research center nearby. However, Rathaway learns that it is actually a Checkmate outpost and warns Oliver before being shot by one of the agents and killed. Oliver, Gemini and Mahkent escape in a snowmobile, while Blockbuster attempts to leave them behind and is killed when Waller orders the entire outpost to be destroyed, with the agents still inside.
Oliver, Gemini and Mahkent return to Star City in a freight boat, where Gemini reveals she has a five-year-old daughter, Rouge, that she wants to rescue. Oliver promises to help her.
In Star City, Mahkent leaves, and Oliver and Gemini meet with Hackett, and he informs the police of their location. A SWAT unit interrupts their meeting, and Oliver and Gemini escape to a nearby safe house, where Oliver retrieves his equipment and decides to go after Hackett.
Meanwhile, at the SuperMax, Merlyn is interrogated by Waller, who tortures him into revealing he was hired by Cross and Hackett to frame Green Arrow of murdering Khalid. Waller sends her men to Star City.
Green Arrow attacks Hackett's office, where they fight. Hackett reveals that he attempted to murder Oliver three years prior, leading to Oliver ending up on the island. Oliver is preparing to kill Hackett when Waller's men arrive. He instructs Gemini to escape and spares Hackett, surrendering to Waller's forces.
Hackett visits Oliver at the SuperMax and confirms his participation in the plan, believing all evidence of it to be destroyed, but Oliver reveals that Gemini stole copies of their plans from Cross and leaked them to the press.
Hackett is arrested by the FBI, while Oliver is released. He exposes Waller's crimes, including the violation of the inmates' human rights and a series of needless murders, and Waller is fired from the government, while Cross commits suicide to avoid being arrested.
Gemini is forced to turn herself in once more and complete her sentence at the SuperMax, but Oliver arranges for it to be reduced due to her contribuition to clear his name, and reveals that he has adopted Rouge and is proving her with a good life while Gemini is in prison.
Oliver and Gemini kiss before Oliver returns to Star City with Rouge and resumes his activities as Green Arrow.
