Half-Life 2
Physicist Gordon Freeman is awoken from stasis by the mysterious G-Man, some years after Gordon and other scientists accidentally opened a portal to a dimension of hostile aliens at the Black Mesa Research Facility. The event attracted the attention of the Combine, a multidimensional empire whose technological superiority allowed them to conquer Earth in seven hours. The Combine have implemented a brutal police state by biologically assimilating humans and other species, and prevent humans from breeding via a "suppression field". The G-Man inserts Gordon into a train arriving at City 17, site of the Combine Citadel, where Dr. Wallace Breen, the former Black Mesa administrator who negotiated Earth's surrender, governs as the Combine's puppet ruler.
After eluding Combine forces, Gordon joins resistance members including Barney Calhoun, a former Black Mesa security guard working undercover as a Combine police officer; Dr. Eli Vance, former Black Mesa scientist and leader of the resistance; Alyx Vance, Eli's daughter; and Dr. Kleiner, an eccentric Black Mesa scientist. After a failed attempt to teleport to the resistance base, Black Mesa East, from Kleiner's makeshift laboratory, Gordon progresses on foot through the city's canal system. After obtaining an airboat, he battles his way to Black Mesa East, several miles from the city.
Gordon is reintroduced to Eli and meets another resistance scientist, Dr. Judith Mossman. Alyx introduces Gordon to her pet robot D0g and gives him a "gravity gun", an instrument which can manipulate large objects. Black Mesa East comes under Combine attack, and Eli and Mossman are taken to Nova Prospekt, a Combine prison. Separated from Alyx, Gordon detours through the zombie-infested town of Ravenholm, assisted by its last survivor, Father Grigori. Escaping the town, Gordon discovers a resistance outpost, and uses a customized dune buggy to travel a crumbling coastal road to Nova Prospekt, encountering Combine patrols and helping the resistance fend off raids.
Gordon lays siege to Nova Prospekt by using pheromone pods to command the hordes of alien antlions that infest the coast. He reunites with Alyx in the prison and they locate Eli, but discover that Mossman is a Combine informant. Before they can stop her, Mossman teleports herself and Eli back to City 17's Citadel. The Combine teleporter explodes as Gordon and Alyx use it to escape Nova Prospekt.
Returning to Kleiner's lab, Gordon and Alyx learn that the teleporter malfunctioned and that a week has passed. During their absence, the resistance has mobilized against the Combine. In battle, Alyx is captured by the Combine and taken to the Citadel. Gordon fights his way to the Citadel with the aid of D0g and Barney. There, he is caught in a Combine "confiscation chamber" which destroys all his weapons except the gravity gun, which is inadvertently supercharged by the forcefield, allowing him to pick up Combine soldiers.
Gordon is captured in a Combine transport pod and taken to Dr. Breen's office, where he and Mossman are waiting with Eli and Alyx in captivity. Breen explains his plans for further conquest of humanity by the Combine, contrary to what he had told Mossman. Angered, Mossman frees Gordon, Alyx, and Eli before Breen can teleport them off-world. Breen tries to escape through a portal, but Gordon destroys the portal reactor with the gravity gun. Just before the Citadel is destroyed in an ensuing explosion, time is frozen. The G-Man reappears, praising Gordon for his actions in City 17. Making vague mention of "offers for [Gordon's] services", the G-Man places him back into stasis.
alternate reality, sci-fi