A war between two factions outside the Solar System threatens Earth. A wayward missile in that war hits the sun (and destroys a starliner en route), and this causes the sun's nuclear fusion to go out of control. In one Earth year, unless the fusion is corrected, the sun will burn the Earth and all life will cease to exist. Also, in three years, the sun will explode and destroy the solar system. The Argo, now officially captained by Derek Wildstar, is commissioned (with new cadets) to search for a new home for the people of Earth.

On board the Argo, Commander Wildstar meets former shipmate Cory Conroy. Derek shows Conroy the new Cosmo Tiger fighter, being piloted by Cadet Flash Contrail. In the mess hall, they meet Flash briefly before Derek receives orders to send Flash back home. Mark Venture briefs the crew on where they plan to look for a new planet, but Derek says that beyond a certain point they don't know what to expect. The ongoing war between the two factions intrudes into Earth's solar system, prompting the Earth Defense Force commander to order the Argo to launch sooner than the six days Wildstar said he needed to prepare for departure. Meanwhile, the increasing solar activity creates more havoc on the Earth. When Flash gets home, he argues with his father, who wants him to take over the family business. Flash's ill mother implores his father to let him return to the Star Force so he can be happy.

During the ongoing war outside of Earth's solar system, one of the ships mistakenly warps to Earth's atmosphere, heading directly for the Argo's location. The Earth Defense Force alerts Commander Wildstar, who sends the Cosmo Tigers to investigate. The ship attacks the Tigers, but they dispatch it. Wildstar briefs his crew on the mission, offering those who wish to remain on Earth a chance to leave. Chief Communications Officer Homer Glitchman is the only one who does so, wanting to find a girl who had given him a flower, but whose name he didn't get. Derek discovers that the girl in question is Wendy, the EDF's commander's granddaughter, and sends out the Cosmo Tigers to bring Homer back. Just then, he finds Homer still on board and brings him back to meet Wendy, who wishes him luck. As the Argo launches into space, 329 days remain before the sun destroys Earth.

Commander Wildstar orders a warp to the planet Mars to test the crew. As soon as the ship comes out of warp, he has the crew go through sixteen hours of drills, including a simulated attack on Mars and the Argo taking damage and casualties. While the exhausted cadets rest, Jason discovers that the section commanders continue to train even after drills are completed. He also learns that Wildstar trains harder than anyone else, even in his spare time. Just then, the crew are summoned to their battle stations when the ship's radar picks up enemy missiles approaching. The Argo destroys all the missiles and continues on its journey. 328 days remain before the sun destroys Earth.

The Argo approaches the battle-damaged Legendra, fleeing from the Galman fleet. Wildstar wishes to keep Earth neutral, but the Galmans have other ideas.

Dagon continues his attack on the Argo and the Legendra near Planet Brumas. The Cosmo Tigers destroy several Galman ships, and Dagon ramps up the attack. Ram sends one final message thanking the Argo for its help before the Legendra is destroyed. Commander Wildstar orders the Cosmo Tigers back before continuing the counterattack on the Galman fleet. Dagon orders his flagship and two others to warp while the remaining ships continue to engage the Argo. One ship crashes into the Argo, inflicting heavy damage. A Galman boarding party engages the Argo's KP crew, mortally wounding Jason's supervisor. Jason grabs several weapons and helps hold off the boarding party. Wildstar leads a team to help, and Jason kills his first combatant -- a Galman robot. The Argo pulls free from the Galman ship before the latter explodes. On the Argo's main deck, Wildstar offers a space burial to those who died in the attack, including Jason's supervisor and several non-robotic Galmanians. 325 days remain before the sun destroys Earth.

As the Argo approaches one of Neptune's moons, which is similar to Earth, an attempt on Earth to use the sun's energy to cool it off fails. Meanwhile, Commander Wildstar heads a landing party to locate the source of several radio transmissions coming from the planet. Just then, the party encounters fire from a lone gunman, and they pursue the man, who appears to be from Earth. They find the man, his daughter, and her husband, the latter of whom is seriously ill and eventually dies. When the man collapses, the team transports him and his daughter back to the Argo. On the other side of the planet, Dagon prepares to attack the Star Force with an array of ships designed to reflect lasers fired from the planet's surface at their target. He activates the weapon, attacking the Argo from all sides. Wildstar heads off to locate the base and destroy it. 308 days remain before the sun destroys Earth..

As Dagon continues his attack on the Argo, Derek Wildstar tries to locate the Galman base. He discovers that Galman ships, not satellites, are reflecting the lasers toward the Argo, and launches an attack on them. The Cosmo Tigers provide additional support, destroying the ships. Derek locates the relay stations and orders a surprise attack. Dagon launches a proton missile at the Argo, but the Star Force fires the Wave Motion Gun, destroying both the missile and the base. Dr. Sane tries his best to save the old man rescued from the planet, but is unsuccessful. Derek then learns that the woman he rescued from the planet is four months pregnant and decides to send all the women on the ship, except for Nova, back to Earth. 306 days remain before the sun destroys Earth.

As the hijackers take over the Argo's engine room, Jason and Flash discover they are carrying stun rifles and report this to Commander Wildstar. The hijackers demand to be taken to the planet Guardiana and its Queen, who is said to be a legendary space goddess. Leading a team into the engine room, Derek overpowers the hijackers, turning them over to the Bolars. Bemlayze, the Bolar Prime Minister, arranges for Derek to meet him on Berth. Enroute, Derek discovers the hijackers are being executed. He then learns that Bemlayze had ordered their execution. When Derek says he'll rescue the prisoners, the meeting turns sour, forcing Derek and his crew to fight their way out of the meeting and off the planet. In space, Bemlayze's ships attack the Argo but miss and end up destroying Berth. Derek vows to never forget Bemlayze's cruelty. 227 days remain before the sun destroys Earth.

On board the Argo, Dr. Sane operates on Commander Wildstar to remove shrapnel from his arm. When Derek wakes up, he tries to go to the bridge, but Nova orders him to rest, saying she'll take care of him. Meanwhile, Sandor finishes the subspace sonar and installs it on the ship. In space, Feral has two of his ships move into position so they can be detected. The Argo destroys both ships, but the rest of the fleet then lures it to Admiral Smeardom's fortress. With Derek incapacitated, Jason orders an attack, but Smeardom captures the Argo. Upset at the result, Jason visits Derek in the infirmary to apologize. Derek, however, consoles the cadet, telling him not to be discouraged. He then asks Jason to help him to the bridge. Smeardom reports the Argo's capture to Galman Emperor Desslok, but when Desslok hears the Argo's name for the first time, he berates Smeardom for disobeying orders. Desslok radios the Argo and apologizes for Smeardom's actions. He invites the Star Force to visit him at the center of the Galman Empire, not as a prisoner, but as a guest. 207 days remain before the sun destroys Earth.

Sandor and Homer travel to Earth with Major Cranshaw, one of Desslok's scientists. After meeting the Earth Defense Force's commander, Cranshaw takes one ship to Saturn while Sandor and Homer follow in a second ship. Sandor explains the plan: first, Cranshaw will launch specially designed missiles to form a magnetic shield around the sun. Then Sandor's group will launch special missiles to gather asteroid fragments and send them into the sun. Finally, Cranshaw will launch proton missiles, and the resulting reaction will return the sun to normal. At first the plan appears to succeed, with the sun's temperature falling, but it then rapidly rises, forcing both ships to immediately retreat. Humiliated by the failure, Cranshaw orders his men to abandon his ship, then commits suicide by flying it into the sun. Derek and Nova offer their condolences to Desslok on the loss of Major Cranshaw. Desslok wishes Derek and Nova success on their mission. As Derek and Nova leave, they see several of Queen Guardiana's worshippers. Derek asks Desslok about the worshippers, and Desslok simply says Galman doesn't need two gods. He then tells the Star Force about another planet -- Phantom -- which is similar to Earth and supposedly uninhabited. 153 days remain before the sun destroys Earth.

The Argo begins the first of three warps to Planet Phantom, a distant planet of which little is known other than that it resembles Earth. At Bolar Headquarters, Belmayze orders a fleet to attack and destroy the Argo. Meanwhile, the Star Force receives a distress call from a small planet. Commander Wildstar sends Jason, Flash and IQ-9 to investigate, but just as they leave the Argo, the transmission stops. Derek decides to allow the mission to continue. On the planet, Jason and Flash discover several followers of Queen Guardiana who were on a pilgrimage when their ship became disabled and they had to land. Derek has a team repair the pilgrims' ship, but Bolar ships appear just after the pilgrims take off. Derek tries to negotiate with the Bolar fleet, but the fleet attacks both the Argo and the pilgrims' ship. Derek has the Cosmo Tigers launch to protect the pilgrims' ship. Just then, Queen Guardiana appears before the Argo in the direction of Phantom. The Star Force wonders if she might perhaps be guiding them toward the planet. 139 days remain before the sun destroys Earth.

On board the Argo, Derek, Nova and Sandor are unable to locate Flash and Jason, who are trapped in a tunnel on the planet. Suddenly, Flash and Jason meet the planet's life center, who asks them to take care of Queen Mariposa. Phantom says that Mariposa has the secret to the planet Guardiana and must be taken somewhere safe. Phantom then returns Flash, Jason and Mariposa to the planet's surface, where a rescue ship from the Argo picks them up. They describe their findings to Derek, who assigns Flash to be Mariposa's escort. After the Star Force leaves, they see Galmanian ships materialize. Mariposa says that the Galmans will attack Phantom. Flash warns Derek, who sends an urgent message to the Galmans asking them not to attack. The message is ignored, however, and the Galmans destroy Phantom. Derek asks Desslok why he ordered Phantom destroyed. Desslok says that he punished Phantom for embarrassing him and Derek by deceiving them. Having lost much time, the Star Force resumes its search for a new Earth. Meanwhile, Belmayze and Desslok learn that Mariposa is now on board the Argo and dispatch war fleets after the ship. 111 days remain before the sun destroys Earth.