The first episode of Red vs. Blue introduces the main characters, and poses the all-important question, why are we here?

The Reds get a new piece of equipment, and Grif has a problem with its name.

The Red and Blue armies get new recruits.

Caboose is given the job of "guarding the flag". Donut goes to the store.

Donut returns from the store with a surprise.

The Blues go through the teleporter. The Reds get the upper hand.

While Church and Tucker lament their current situation, Caboose hops into the tank.

Grif and Simmons flee as Caboose's trigger happy firing has dire consequences.

The cavalry arrives, and Caboose gets stuck.

Tucker requests reinforcements, and gets more than he bargained for.

Tex assaults the Red Base, injuring donut and knocking out Grif and Simmons.

Church reveals that Tex was his former girlfriend and the Red Team airlifts a severely injured Donut back to headquarters.

Simmons and Grif guard Tex while Church explains to the Blues about Tex's AI.

The Blues fake an attack on the Reds in order to free Tex and inadvertently get Sarge shot in the head.

Sarge and Church meet up in the spirit world and talk about the afterlife until Sarge is revived by Grif.

Donut returns with new armor, and Lopez finally speaks.

The origin points here.

Church tries to warn the Red Team of Tex's impending attack.

The final episode of Red vs. Blue season one.

Church discovers a note from Sheila and Lopez confirming that they have started a robot army. At the Red Base, Sarge unveils the two new robots; one contains a microphone to spy on the Blues, and the other contains a bomb. The Reds and the Blues meet in the center of the gulch to execute the exchange. Sheila and Lopez also arrive to conquer the Blues; Lopez becomes angry at seeing new robots brought into the conflict, and rushes forward to attack. A tense Mexican standoff results, and Sarge tries to call an air strike. However, due to crossed communication channels, Tucker intercepts his message, and realizes that Vic is apparently working for both Red and Blue Commands. While Church possesses one of the robots, Tucker tries to alert everyone that Red and Blue are the same, but is hit by a rocket before anyone can understand him. His attacker is apparently Doc, possessed by O'Malley, who flies around on the hovercraft, firing rockets at will. In the ensuing chaos, O'Malley takes Lopez as a hostage, announces his intention to conquer the universe, and disappears through the Red Team's teleporter. The Reds and Blues call a temporary truce to pursue Doc, whom the Blues need to heal Tucker, and to retrieve Lopez, whom the Reds need for the plans his memory contains. Donut, Sheila, Tucker, and one of the robots remain behind in the gulch while everyone else follows through the teleporter. Tex soon surfaces in the remaining robot body. Unfortunately, due to a teleporter malfunction, the pursuing Reds and Blues end up separated and scattered across different places. Simmons ends up in a huge area full of teleporters, Church and Grif end up captured by Max Gain, a member of the Red team in Sidewinder, and Sarge and Caboose appear in the stream in Battle Creek.

O'Malley berates Lopez for creating such a slow moving army. In revenge, Lopez tricks O'Malley into insulting himself in Spanish. The Reds flee the battle in the Warthog to track down the distress signal. Donut is left behind to discourage pursuit, but manages to steal O'Malley's hovercraft and rejoin his teammates. Tex steals Tucker's sword so she can fight the robots; Church decides that she must be The Great Destroyer from the prophecy. An unseen figure wipes out O'Malley's army with a volley of plasma grenades, and then attacks a startled O'Malley. Lopez's fate is left unrevealed. Shortly after Donut catches up with the other Reds in a cave, Simmons and Grif track the signal out of the cave, finding themselves back in Blood Gulch (Coagulation in Halo 2). This discovery is accompanied by a lengthy scream of "Noooooooooo!" from Grif. Back at the fortress again, Church and Tucker admire the slaughtered robots and congratulate Tex, but she admits she's not responsible: she was in the basement, trying to get the sword to work. Church rushes over to Gary to question him about the identity of The Great Destroyer, unaware that an Alien is sneaking up on him.

Church returns to the Blue Base where Junior, the baby to which a now-comatose Tucker has given birth, is wreaking havoc off-screen. Church and Doc argue about the child until a spaceship crashes into the gulch on top of Donut; Church leaves to investigate. The Reds bicker about rescue plans until Sarge leaves to fetch a rescue device. Church arrives and claims the ship with Sheila's support.

As Church argues with Simmons and Grif, a tapping noise begins to sound from the ship. Sheila abruptly leaves, forcing Church to retreat to the base.

Church attempts to call Vic for reinforcements, but is stalled by an elaborate answering machine system. Meanwhile, the back door of the ship opens, and an unseen entity emerges.

Church finally discovers that Vic's voice mailbox is full. The Red reinforcement who emerged from the ship is revealed to be the Sister of Grif, who by Simmons' theory arrived using the ship's light drive, which caused her and the ship to move forward in time as it was traveling to Blood Gulch. Meanwhile, it is revealed that Donut fell into an underground cave (Waterworks in Halo 2) after the ship crashed on top of him.