Spider-Man 3 opens in New York City, about a year after the heroic sacrifice of Otto Octavius, known as Doctor Octopus. The city is alive with celebration during a festival honoring Spider-Man for saving Gwen Stacy's life. Peter Parker, the man behind the mask, is basking in the glow of his heroism but carries a quiet hope: he plans to propose to Mary Jane Watson, his longtime love, who has recently made her Broadway debut. The atmosphere is festive and hopeful as Peter and Mary Jane share a tender moment, their future seemingly bright.

One evening, while Peter and Mary Jane are on a date in Central Park, a sudden meteorite crashes nearby, shattering the calm. From the smoking crater seeps a strange, black, oily extraterrestrial symbiote. It slithers silently, attaching itself first to Peter's motorcycle and then following him back to his apartment. Unbeknownst to Peter, this alien entity waits patiently until he falls asleep, then bonds with his Spider-Man suit, transforming it into a sleek, black version that clings to his body like a second skin.

Peter wakes the next morning hanging from a skyscraper in Manhattan, his suit now black and glossy. He immediately notices his powers are enhanced--he swings faster, hits harder, and his agility is heightened. But with this power comes a darker change. The symbiote amplifies Peter's aggression and arrogance. His once humble and kind demeanor gives way to a more vengeful, selfish, and cocky persona. He struts through the city, taunting criminals with a newfound confidence and even publicly humiliates Mary Jane, who is struggling with her faltering career. At a jazz club, Peter performs a provocative, almost mocking dance to spite Mary Jane, his actions pushing a wedge between them.

Meanwhile, Harry Osborn, Peter's old friend and son of the late Norman Osborn, is consumed by revenge. Harry knows Peter is Spider-Man and blames him for his father's death. Using his father's Green Goblin technology and performance-enhancing gas, Harry dons the mantle of the new Green Goblin. His attacks on Spider-Man are fierce and personal. Their brutal confrontation at the Osborn mansion leaves Harry defeated and suffering from partial amnesia after a fall from his glider. For a time, the two resume their friendship, Harry unaware of his Green Goblin persona.

Parallel to these events, Flint Marko, an escaped convict, is on the run. He visits his wife and sick daughter, desperate to provide for them. In a fateful moment, Marko falls into an experimental particle accelerator, which fuses his body with the surrounding sand, granting him the ability to manipulate sand and transform his form at will. He becomes the formidable Sandman, a living sandstorm of destruction.

Peter discovers a shocking truth when NYPD Captain George Stacy, Gwen's father, informs him and Aunt May that Flint Marko--not the initially suspected Dennis Carradine--is the true killer of Peter's Uncle Ben. This revelation shakes Peter to his core, fueling his determination to bring Marko to justice. Spider-Man tracks Marko to an underground subway tunnel, where they engage in a fierce battle. Peter learns that water can weaken Marko's sand body and cunningly rips open a large water pipe, dousing Marko and reducing him to mud. Yet, Marko escapes, leaving behind a trail of chaos.

As Peter's darker side grows under the symbiote's influence, his relationships crumble. Mary Jane breaks up with him, confessing she is in love with another man. That man, Harry Osborn, reveals himself in a tense restaurant confrontation, claiming the role of her new boyfriend. Peter confronts Harry at the Osborn mansion, where they engage in a brutal fight. Empowered by the black suit, Peter ultimately defeats Harry, leaving him wounded and bitter.

Recognizing the symbiote's corrupting hold, Peter struggles internally before finally ripping it from his body in a moment of painful clarity. The alien creature, rejected and vengeful, finds a new host in Eddie Brock, a disgraced and bitter photographer at the Daily Bugle who holds a deep grudge against Peter. Bonded with the symbiote, Eddie transforms into Venom, a monstrous and powerful adversary with abilities mirroring Spider-Man's but fueled by hatred.

Venom seeks out Flint Marko, convincing him to join forces against Spider-Man. Together, they become a formidable threat. Venom abducts Mary Jane, holding her captive at a construction site, while Marko uses his powers to keep the police at bay. Peter arrives to confront them but is outmatched. Harry Osborn, having recovered his memories and understanding the truth about his father's death--that Peter was not responsible--arrives with his Green Goblin gear to aid Peter.

The final battle erupts at the construction site, a chaotic clash of powers and wills. Venom attacks Peter with ferocity, attempting to impale him with Harry's glider. In a heroic act of redemption, Harry leaps in front of the attack, taking the fatal blow himself. The glider impales Harry, and he dies in Peter's arms, his last act saving his friend.

Fueled by grief and determination, Peter uses high-frequency sound waves, exploiting the symbiote's vulnerability to sonic attacks. He creates a perimeter of metal pipes to amplify the sound, weakening Venom and forcing the symbiote to separate from Eddie Brock. Peter then hurls a pumpkin bomb, a signature weapon from the Green Goblin arsenal, at the symbiote, vaporizing it and ending Venom's threat.

Sandman, battered and remorseful, reveals the truth behind Uncle Ben's death: it was an accident, a tragic mistake that has haunted him ever since. His criminal acts were driven by a desperate desire to help his sick daughter. Peter, moved by this confession, forgives Marko, who escapes into the night, free but changed.

The film closes with Harry's funeral, a somber moment of loss and reconciliation. Peter visits Mary Jane at the jazz club where she works. They share a heartfelt embrace and a dance, signaling healing and hope for their future together. The city breathes again, Spider-Man's battles behind him, but his journey far from over.

At the end of Spider-Man 3, Peter Parker confronts the symbiote that has taken over his life, leading to a final battle with Venom and Sandman. After a fierce fight, Peter is able to defeat Venom with the help of his ally, Gwen Stacy, and ultimately forgives Sandman for his past crimes. The film concludes with Peter choosing to embrace his responsibilities as Spider-Man, reconciling with Mary Jane Watson, and moving forward with a sense of hope.

Now, let's delve into the ending in a more detailed, chronological narrative.

As the climax of Spider-Man 3 unfolds, Peter Parker, now fully aware of the destructive influence of the symbiote, resolves to confront the darkness that has consumed him. The scene shifts to a dark, abandoned church bell tower, where Peter faces Eddie Brock, who has been transformed into Venom by the symbiote. The atmosphere is tense, filled with the echoes of their past confrontations and the weight of their shared history. Peter, burdened by guilt and anger, prepares for a showdown that will determine not only his fate but also the fate of those he loves.

In a dramatic confrontation, Venom taunts Peter, revealing his plan to kill Mary Jane Watson as a means of revenge. The stakes are high, and Peter's heart races with fear for Mary Jane's safety. As the battle ensues, the church bells toll, creating a cacophony that disrupts the symbiote's hold on Eddie. The sound causes Venom immense pain, and Peter seizes the opportunity to fight back. With a combination of agility and determination, he manages to weaken Venom, ultimately leading to Eddie's demise when he is consumed by the symbiote's own destructive nature.

Meanwhile, the scene shifts to a nearby construction site where Sandman, who has been revealed to be a tragic figure with a complicated past, is also facing his own reckoning. Peter confronts him, and in a moment of vulnerability, Sandman reveals that he was only trying to save his sick daughter, explaining his criminal actions. This revelation stirs something within Peter, who grapples with his own sense of justice and forgiveness. Instead of delivering a final blow, Peter chooses to let Sandman go, understanding that vengeance will not bring him peace. Sandman, touched by Peter's mercy, departs, leaving behind a sense of unresolved conflict but also a glimmer of hope for redemption.

The film then transitions to a quieter moment, where Peter and Mary Jane finally reconcile. After the chaos and turmoil, they find themselves in a serene setting, where Peter expresses his commitment to being a better person and a better Spider-Man. The emotional weight of their relationship is palpable, as they embrace, symbolizing a fresh start and a renewed bond. Peter's journey has taught him the importance of love, responsibility, and the power of forgiveness.

As the credits roll, the audience is left with a sense of closure for the main characters. Peter Parker, having faced his inner demons and external foes, emerges stronger and more self-aware. Mary Jane, having endured her own trials, stands by his side, ready to face the future together. Sandman, though still a flawed character, is given a chance at redemption, hinting at the complexities of human nature. The film concludes with Peter swinging through the city, embodying the spirit of Spider-Man, a hero who has learned that true strength lies not just in power, but in compassion and understanding.

In "Spider-Man 3," there is no traditional post-credit scene that teases future films or storylines. However, the film concludes with a poignant moment that serves as a thematic resolution.

After the climactic battle with Venom and the Sandman, Peter Parker, portrayed by Tobey Maguire, reflects on his journey and the lessons learned about responsibility, forgiveness, and the consequences of his actions. The final scene shows Peter and Mary Jane Watson, played by Kirsten Dunst, reconciling and sharing a dance together in a quiet, intimate setting. This moment encapsulates the emotional growth of both characters, highlighting their love and the hope for a brighter future together.

The film ends on a note of redemption and healing, emphasizing the importance of moving forward and embracing the light after darkness, rather than setting up any future plotlines.

Peter Parker's aggressive change in personality is primarily caused by the influence of the black symbiote, which he encounters after a meteorite crashes to Earth. The symbiote enhances his powers but also amplifies his darker emotions, leading to a more arrogant and vengeful version of himself. This transformation is visually represented through his new black suit, which contrasts sharply with his traditional red and blue Spider-Man costume.

Harry Osborn's relationship with Peter Parker is tumultuous in Spider-Man 3. Initially, Harry seeks revenge against Peter for his father's death, believing Peter betrayed him. This leads to intense confrontations, including a dramatic fight where Harry, as the New Goblin, attacks Peter. However, as the story progresses, Harry learns the truth about his father's demise and ultimately reconciles with Peter, sacrificing himself to save him from Venom, showcasing a complex mix of friendship, betrayal, and redemption.

Eddie Brock's transformation into Venom is driven by his intense jealousy and resentment towards Peter Parker, whom he blames for his failures. After losing his job as a photographer due to Peter's actions, Eddie's anger festers, especially after discovering Peter's relationship with Gwen Stacy. When he encounters the black symbiote, he bonds with it, becoming Venom, which amplifies his desire for revenge against Spider-Man, leading to a dark and vengeful character arc.

Gwen Stacy, portrayed as a new character in Spider-Man 3, serves as a significant influence on Peter Parker's emotional state. Initially, she is a love interest for Peter, which creates tension in his relationship with Mary Jane Watson. Peter's interactions with Gwen, especially when he kisses her in front of Mary Jane, lead to feelings of jealousy and insecurity for Mary Jane. Gwen's presence ultimately complicates Peter's life, contributing to his internal struggles and the darker path he takes under the influence of the symbiote.

The final battle against Sandman and Venom is a climactic showdown that takes place in a construction site. Peter Parker, with the help of Harry Osborn, confronts Sandman, who has the ability to transform his body into sand and grow in size. The fight is intense, with Peter struggling against Sandman's powers. Meanwhile, Venom, who has captured Mary Jane, adds urgency to the battle. The scene is filled with high stakes, emotional tension, and visual effects as Peter and Harry work together to defeat their foes. Ultimately, Harry sacrifices himself to save Peter, allowing him to defeat Venom and Sandman, leading to a resolution of their conflicts.

"Spider-Man 3" contains several elements that may be considered objectionable or upsetting for children or sensitive viewers. Here are some aspects to be aware of:

1. Violence and Action Sequences: The film features intense action scenes, including battles between Spider-Man and various villains. These sequences can be quite dramatic and may include physical confrontations that could be frightening for younger viewers.

2. Dark Themes: The movie explores themes of revenge, jealousy, and the struggle between good and evil. Characters experience emotional turmoil, which may be heavy for some audiences.

3. Character Downfalls: There are moments where characters face significant personal challenges, including betrayal and moral dilemmas. This can lead to feelings of sadness or discomfort.

4. Emotional Distress: Several characters experience heartbreak and loss, which may evoke strong emotions. The portrayal of these feelings can be intense and may resonate deeply with sensitive viewers.

5. Mature Relationships: The film includes romantic subplots that involve misunderstandings and conflicts, which may not be suitable for younger audiences.

6. Supernatural Elements: The introduction of the symbiote, which influences Spider-Man's behavior, can be unsettling. Its dark and menacing nature may be frightening for some children.

These elements contribute to a more mature tone in "Spider-Man 3," making it potentially less suitable for very young viewers or those who are sensitive to such themes.