Spoiler warning! This section of the article contains spoilers, or hints about the game's storyline or progression.
You might want to skip down to the next heading if you do not want facts about the game's storyline or plot revealed to you.
Throughout the course of Half-Life 2, you will encounter many different major characters. Many play a crucial role in the story of the game.
Dr. Gordon Freeman
Gordon Freeman is the main protagonist of Half-Life 2, who has just escaped the Black Mesa Incident due to the efforts of the G-man. He is currently twenty-seven years old and a young graduate of MIT. Gordon is obsessed with the idea of teleportation and made it his life's ambition. Bored with the slow pace of teleportation research, he eventually received a job at the Black Mesa Research Facility in New Mexico with the help of his mentor, Dr. Issac Kleiner. Moving into Black Mesa, Gordon began working in higher and more classified projects, eventually working on Xen teleportation techniques. During one of the most critical tests, a resonance cascade occurs, springing forth the Black Mesa Incident; Gordon barely survived this event, and was forced to collaborate with G-man or face certain death. Currently Freeman is in stasis and does not know where his next destination lies or what his true destiny is.
The G-man is a very mysterious character who's true intentions are not known at this time. Throughout the Black Mesa Incident, Gordon spots the G-man in various locations around the facility, watching and waiting for him. Towards the end of the game, the G-man finally comes to Gordon and offers him two choices: to work for him or to fight a battle which cannot be won. Half-Life 2 assumes that the choice to work for the G-man was selected; now G-man serves as Gordon's employer, whose intentions for him are unknown.
Alyx Vance is the young daughter of Eli and Azian Vance. She is very intelligent, sympathetic, and extremely independent, as she likes to do things her own way and rebels authority. She meets Gordon in the beginning of the game and quickly becomes friends with him (however, no sensual relationship is involved). Alyx is also friends with Barney Calhoun, Issac Kleiner, and Judith Mossman (although she can be stubborn with Dr. Mossman at times). She also has a robot companion named Dog and serves as a vital figure in the resistance of the Combine.
D0g is Alyx Vance's robot companion, who was built by Eli Vance when Alyx was very young. D0g started out as a small four-foot robot but over the years Alyx added more and more parts to him. He is very intelligent and acts friendly toward the player and others around him. Dog serves as the protector and guardian of Alyx, as he is extremely strong and uses a tractor beam like the one found on the gravity gun.
Dr. Wallace Breen
Dr Wallace Breen was administrator of Black Mesa, and was mentioned but never seen in the original Half Life. It is believed he was tricked by the Combine into allowing the ill-fated test to go ahead and open up the portal to Xen, letting the Combine through. After the Seven Hour War, Breen negotiated a truce with the Combine, who in turn granted him control of Earth. He is apparently in command of the Combine forces on Earth, but he is almost certainly a puppet dictator.
Barney Calhoun is an old friend of Gordon and worked as a security guard at Black Mesa. Trapped in an elevator during the resonance cascade he fought his way to the surface of the facility to escape. Barney has apparently moved to City 17 with the Vances and works undercover for the resistance, having infiltrated the Metro Cops. It should be noted that all security guards in the original Half Life look like Barney, but Valve have revealed that the “real” Barney is the guard seen banging on the door in Black Mesa Inbound.
Dr. Eli Vance
Eli Vance was Gordon’s boss during his tenure at Black Mesa and was in charge of his research team along with Dr. Kleiner due to his unquestionable scientific genius. He has only one leg, the other presumably lost during the events of the first Half Life. The leader and figurehead of the underground human resistance, he spends his time working on the new teleporter in Black Mesa East, just outside of City 17. Father of Alyx Vance, his daughter was one of only two things he brought out of Black Mesa, the other being a picture of his late wife. Many of the events of Half Life 2 are centered on recovering him after his kidnapping by the Combine.
Dr. Isaac Kleiner, or “Izzy” to Eli was Gordon’s mentor and teacher at MIT and the man who helped Gordon get a place at Black Mesa. Although never seen in the original Half Life the model is obviously based on the bald scientists of Black Mesa. He escaped the accident by unknown means and traveled with the Vances to City 17, where he set up his lab in the city and built a teleporter to safely move rebels out of the Combine controlled area. Dr. Kleiner is used primarily for comic relief in the game.
Lamarr is Kleiner’s pet debeaked, harmless headcrab, who it seems Barney hates. Partial to watermelon, it is Lamarr who causes the teleporter accident that prevents Gordon reaching Black Mesa East during Red Letter Day. Lamarr is possibly named for Hedy Lamarr, noted actress and inventor, hence the line “Hedy come back!”
Dr. Judith Mossman
Judith Mossman works with the Vances at Black Mesa East, and although fond of Eli, it is evident she and Alyx do not get on, with Mossman objecting to Alyx’s light-hearted approach to science. During “Entanglement” it is revealed that she is a traitor and had been working for Breen all along, and delivers Eli to the Citadel. At the end however, forced to choose between Breen and Eli, she chooses the latter, regaining some measure of trust.
Father Grigori is the sole human survivor of Ravenholm. Formerly the priest or vicar of the town, the Combine attack and subsequent zombification of his parishioners has driven Grigori mad. Wielding his Winchester rifle “Annabelle”, Grigori uses traps he built with his spare time to free the people from their living nightmare. He aids Gordon during the “We Don’t Go to Ravenholm” chapter helping him clear the graveyard to reach the mine entrance. His ultimate fate is unknown as he retreats down passage out of the player’s field of view. It is difficult to tell whether he is laughing or screaming, but considering his insanity, probably the former.
Colonel Odessa Cubbage
Colonel Odessa Cubbage is in charge of New Little Odessa, a rebel strong point on Highway 17. He gives Gordon the rocket launcher which is used to fight off the gunship. Earlier in the level, using the Combine binoculars, he can be seen talking with the G-man. Although in command of the outpost, there is some doubt over his military accomplishments, and several rebels can be heard discussing this.