Sonic Adventure 2 - Plot

Plot

After discovering the existence of a secret weapon mentioned in the diary of his grandfather, Gerald Robotnik, Dr. Eggman infiltrates a high-security G.U.N. facility in search of it. This "weapon," a black hedgehog named Shadow who claims that he is the "Ultimate Life Form," offers to help Eggman take over the world, telling the scientist to rendezvous with him at the abandoned Space Colony ARK with more Chaos Emeralds. Shadow proceeds in stealing one of the emeralds, and G.U.N. officials mistake him for Sonic. Shadow has a flashback during these events to the final moments of a young girl named "Maria," begging him to do an unspecified task—which he interprets as a request for revenge. Sonic is arrested shortly after he confronts Shadow, who demonstrates to Sonic the Chaos Control technique.

Meanwhile, Knuckles confronts both Rouge the Bat and Eggman, who each attempt to steal the Master Emerald. Knuckles shatters the Master Emerald to prevent this, and proceeds to search for the scattered shards and restore the Emerald. While Rouge also intends to collect the shards for personal benefit, she must also accomplish a mission for the government to spy on Eggman. This mission causes her to infiltrate Dr.Eggman's base, which also leads her to the ARK, where Shadow relays to Eggman his plan to use the Chaos Emeralds to charge a "super weapon" on the ARK called the Eclipse Cannon to take over the world. To accomplish this, Shadow and Eggman recruit Rouge to assist in the search of the Chaos Emeralds.

Tails and Amy infiltrate Prison Island and rescue Sonic from G.U.N., while Eggman, Shadow, and Rouge collect three Emeralds on the island, which they then destroy. Eggman then broadcasts his threats across the planet and demonstrates the cannon's level of power by destroying half of the moon. Sonic and company use the final Emerald within their possession to track down the other six, with Knuckles coming along as well. Together, the group infiltrates Eggman's base, narrowly boarding Eggman's shuttle as it launches into space. Along the ride into space, Knuckles' Master Emerald shards are spilled, and he leaves the group to collect them, encountering Rouge again. During the fight, Knuckles saves Rouge from certain death, and Rouge surrenders her collected shards, finally allowing Knuckles to restore the Master Emerald.

On board the ARK, Tails reveals that he has created a counterfeit Chaos Emerald designed to reverse the effects of the real Emeralds and destroy the Eclipse Cannon. Sonic goes to place the fake Emerald into the cannon when Eggman announces he has captured Tails and Amy. Sonic tries to give Eggman the fake Emerald, but at the last second Eggman traps and jettisons Sonic in an escape pod rigged with explosives. Using the fake Emerald, Sonic manages to perform Chaos Control and escape before it explodes, but Tails, thinking Sonic is dead, fights Eggman again. Shadow is sent to intercept Sonic before he destroys the Eclipse Cannon, but Sonic succeeds.

Once Eggman collects all seven Chaos Emeralds and attempts to fire the Eclipse Cannon at full power, a failsafe activates, and a recorded message is broadcast by the late Gerald Robotnik. It explains that the ARK will collide with and destroy Earth, as revenge against humanity for condemning him and his research, as well as killing his granddaughter Maria and numerous colleagues on board the ARK. Everyone agrees to work together to neutralize the Chaos Emeralds with the Master Emerald and stop the collision. Shadow initially does not participate, due to his apathy for humankind, however Amy's pleading reminds him of Maria's true request to serve as a benefit for society. He catches up with Sonic and Knuckles after they make their way to the core.

After disabling the various security features guarding the Cannon's core, Sonic and Knuckles encounter the Biolizard, a prototype of the Ultimate Life Form, and Shadow's "biological" brother, who had been awoken from stasis to ensure that the Emeralds would not be tampered with. Shadow defeats the Biolizard, allowing Knuckles to deactivate the Chaos Emeralds using his repaired Master Emerald. However, the injured Biolizard uses Chaos Control to fuse with the Eclipse Cannon, becoming the Finalhazard and continuing the ARK's collision course by physically dragging it along. Using the power of the Chaos Emeralds, Sonic and Shadow transform into Super Sonic and Super Shadow and defeat the Biolizard while he is fused to the ARK. They then use Chaos Control to teleport the ARK back into a stable orbit around Earth. The process, however, depletes Shadow's energy, and he is unable to remain in orbit, plummeting to Earth, to his apparent death content that he has fulfilled his promise to Maria. Humanity celebrates openly as the two teams solemnly express gratitude towards Shadow for his sacrifice and return to Earth, expressing their plans from there.