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As Megatron began to thaw, Captain Lennox suggested that they move the All Spark to Mission City, where it would be easier to contact and rendezvous with military airlift to take it to safety. Defense Secretary John Keller agreed with him, despite the risk of attack from pursuing Decepticons. Bumblebee converted the All Spark to a more portable form, and he and a military escort, soon augmented by the Autobots, left for the city.
En route, Optimus Prime left the escort to battle Bonecrusher, while the other Autobots continued into downtown Mission City. Their human allies, meanwhile, had summoned F-22 Air Force fighters to provide aerial support.
Captain Lennox procured several short-wave radios to contact the hoped-for aerial support, intending to summon Blackhawk helicopters to extract the All Spark. They soon sighted a lone F-22 overhead and called for support, marking their location with green smoke. Too late, the Autobots realized that the incoming fighter was in fact Starscream. Ironhide ordered the humans and other Autobots to fall back, as he and Bumblebee lifted a truck to shield them from Starscream's attack. The resulting explosion crippled Bumblebee, severing his legs below the knees.
As the humans realized the deception, they finally heard back from actual incoming Blackhawks, but they then came under attack from Brawl. Ratchet, Jazz and Ironhide all rushed to attack as the human soldiers fell back. Mikaela spotted a tow truck nearby and ran to procure it, while the crippled Bumblebee handed the All Spark off to Sam.
Ironhide rushed Brawl head-on, transforming and vaulting over an extremely hot woman with a huge mouth, all the while dodging two of the Decepticon's missiles. Jazz attacked from another direction, yanking the Decepticon's main gun aside. Brawl transformed and tossed Jazz into a building. Ironhide fired on the Decepticon, while Ratchet and Jazz attacked from both sides, Ratchet using a saw blade to slice off one of Brawl's arms. The humans joined the Autobots in blasting Brawl, until a series of shots from Ratchet knocked the Decepticon to the ground.
While Mikaela worked to hotwire the tow truck, Megatron landed in the city streets, prompting the Autobots to call a retreat. Jazz stayed behind and engaged the much larger Decepticon, getting blasted aside for his efforts.
Mikaela drove the tow truck over to Sam and Bumblebee. Megatron, meanwhile, carried Jazz through the air, crushing him under his feet atop a building, then pulling him out. Jazz fired on Megatron causing his armor to weaken, but the massive Decepticon tore him in half.
On the ground, Captain Lennox's troops observed Brawl getting back to his feet, as well as the arrival of Blackout, who transformed and landed atop a building behind them. Under sporadic hostile fire, Lennox led his troops back to Bumblebee's position as Sam and Mikaela worked to hook Bumblebee to the tow truck. Lennox handed a flare to Sam and ordered him to take the All Spark to a nearby rooftop, while Sergeant Epps summoned their Blackhawk support to pick him up. Ratchet and Ironhide promised Sam that they would protect him as he carried out the mission. After a quick farewell to Mikaela, Sam fled.
Megatron (from somewhere) ordered the Decepticons to attack, prompting Devastator to fire. Ratchet and Ironhide provided cover fire as Sam ran. Blackout attacked from the other side, and Ironhide engaged him. Blackout bashed aside the car that Ironhide tossed at him, then transformed and flew away. Mikaela finished securing Bumblebee and drove him off, as Brawl continued his lumbering advance.
Optimus Prime arrived after his delay on the freeway, transforming and challenging Megatron. Still perched atop his building, Megatron tossed away the remains of Jazz and transformed. He scooped up Prime and took him for a dizzying ride through the streets and buildings of the city, smashing through an entire office building at one point before crashing to the street. The two exchanged their respective views on humanity and fisticuffs. Prime managed to get in a shot at Megatron, but a blast from Megatron's main gun hurled Prime down the street and into the side of another building, prompting viewers to wonder why Michael Bay hates architecture so much. Prime then fell to the street amid a small crowd of panicked humans, some of whom may or may not have been crushed.
With Ratchet and Ironhide alongside him, Sam continued sprinting for the building. Blackout landed in the street and sliced at Sam with his rotor weapon, but did not attempt to capture him. Starscream also landed nearby and engaged Ratchet and Ironhide, blasting them both. Starscream then transformed and launched again as the two Autobots collapsed. Sam continued onwards.
Megatron flew down from the sky and transformed, demanding that Sam give up the All Spark. As Sam darted through traffic, a near-collision with an SUV made him drop the cube, unleashing a pulse of its power. The pulse brought several machines to life, including part of the SUV and a Mountain Dew vending machine.
Sam sprinted into the abandoned building, pursued by Megatron, who smashed through a floor practically on Sam's heels but failed to stop him from entering a fire stairwell.
Mikaela and Bumblebee stopped in an alley, while Sam continued climbing and Lennox's troops continued fighting against Brawl. Mikaela was crying, hitting the wheel in frustration, then turned to look at Bumblebee, who nodded. After a moment of preparation, Mikaela backed the tow truck into the street so that Bumblebee was facing forwards, then drove it full speed in reverse into the battle scene. Under heavy attack from two directions, Brawl suffered heavy damage, before a final shot from Bumblebee hit him in the chest, bringing him down for good. He collapsed into the building where Lennox's troops had taken shelter.
As the Blackhawks closed in, Sam reached the rooftop and activated his flare. Starscream transformed and landed on a nearby building as the helicopters pulled up to the rooftop. Sam was inches away from handing off the All Spark when Starscream shot the waiting Blackhawk out of the sky. Optimus Prime sprinted toward the building, determined to save Sam. Starscream continued watching from nearby while Megatron bashed his way onto the rooftop. Cornering Sam, Megatron demanded the All Spark, then unsheathed a barbed mace and bashed the building out from under Sam's feet when he refused. Optimus Prime, suspended most of the way up the building, caught the falling human. Prime then vaulted/fell down to street level, with Megatron close behind. The two metal titans smashed into the street, scattering still more panicked humans, one of whom got himself flicked aside by Megatron.
Prime ordered Sam to take shelter behind him and to push the All Spark into his chest if he was unable to defeat Megatron. As the two leaders laid into one another a second time, Lennox's troops moved in on their position. They stopped and observed as Blackout transformed, landed, and moved in to assist his leader. Epps called in a full air strike on Blackout and Megatron, advising that the targets would be marked. The troops then marked Blackout with green laser light as the F-22s closed in. Meanwhile, Lennox secured a fallen motorcycle.
Blackout was about to fire when he noticed the lasers lighting him up, so he instead turned to engage the soldiers, opening fire. Lennox raced at him on his motorcycle, evading Blackout's blasts and purposefully going into a long skid/slide along the ground. As Blackout was hit by fire from the F-22s, Lennox slid past and under him, firing several rounds directly up into the Decepticon's chest and crotch. (Ow!!) The Decepticon fell dead to the pavement. Lennox urged his troops onward as Megatron appeared to be getting the upper hand over Optimus.
As a second wave of F-22s approached the city, Starscream appeared in their midst, destroying three of them before the pilots realized what was happening. The surviving pilots attempted to engage the Decepticon. Several of the F-22s survived to make an attack run on Megatron, firing on him while Lennox's troops also attacked him, damaging his chest. Megatron advanced on Sam, and Prime urged him to push the cube into Prime's chest. Instead, Sam opted to push it into Megatron, killing him.
Ratchet and Ironhide arrived then, carrying the remains of Jazz, and Mikaela and Bumblebee reached the scene soon afterward. Prime thanked the humans for their effort and sacrifice. Bumblebee requested to stay with Sam. Prime granted the request, then extracted a sliver of the All Spark from Megatron's body.
Initial media reports called the attack "so-called alien activity" but the US government denied aliens had caused the Mission City destruction.
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