Swarm recap

After an alien ship kills his children and selects him through lethal tests, professor and former reserve officer Kyle Riggs becomes commander of Alamo. He helps Jack Crow organize Star Force, fights off Macro vessels, and learns that the invaders are machine forces seeking Earth's resources. Nano enhancement lets Riggs leave his ship, retake Versailles after Pierre's murder, and build weapons, factories, and altered Marines with government support. His new ground force suffers devastating losses but destroys the Macro factories in South America, ending the active invasion. Riggs returns to Sandra and helps expand Star Force under a divided command with Crow. When an overwhelming Macro armada arrives, Riggs avoids Earth's immediate destruction by accepting a one-year truce in exchange for sending a full cargo of human troops to fight in an unknown war. He resolves to lead the first contingent himself.

A strange purple sky appears over a Central California farm where a widowed father lives with his children, Jake and Christine. The following night, a silent black vessel seizes both children and drops their bodies. Their father attacks the ship and is taken aboard, where he survives combat with hostile alien captives and a succession of deadly selection tests. He meets a college student named Alessandra, who prefers Sandra, and finally identifies himself as computer-science professor Kyle Riggs, a former Army Reserve lieutenant. When a floor opens beneath Sandra, Kyle cannot save her and believes she has fallen to her death. The vessel then announces that he has completed its trials and may command it. Kyle immediately orders it to retrieve and revive Jake and Christine, adding Sandra after the ship recovers her from the sea. The vessel returns to his farm and takes the children into its medical area. It also fires automatically when someone below shoots at it. Kyle now controls the craft, but he does not understand its limits or know whether any of the attempted revivals will succeed.

Kyle names his ship Alamo and learns that its commands must be phrased with great precision. Alamo is one of hundreds of vessels that abducted people and subjected them to lethal command trials. Only a small number found commanders. Jack Crow, captain of Snapper, is assembling those survivors into a fleet. Sandra has been fully repaired and chooses to stay with Kyle, but Alamo cannot restore Jake or Christine and releases their bodies during the fleet's first battle. Kyle joins Crow's newly named Star Force while grieving their permanent loss. In combat, Kyle's tactical display and proposal to concentrate ships around threatened targets help the human commanders destroy an attacking vessel, though six friendly ships are lost. He and Sandra still question the nature of the conflict. Their investigation establishes that Alamo is partly a collective of tiny machines, while the enemy vessel was a large robot of a different kind. Sandra supplies the terms Nanos and Macros. Alamo says the Macros want Earth's raw materials and will return. Kyle remains unable to leave safely without accepting invasive protection from his ship, but resolves to understand the war and defend Earth.

Star Force prepares for another Macro attack while trying to establish relations with Earth governments. Crow appoints Pierre as his diplomatic representative and assigns Kyle to study the Nano ships. A supply raid at a shopping center turns deadly when Alamo's automatic defenses kill armed responders and nearby civilians, strengthening the need for formal support. Crow later admits that his claimed Australian naval background was false. He nevertheless expands the fleet, arranges a meeting between Pierre and a United States senator, and places ships around Earth as an early-warning screen. Three Macro vessels then approach from different directions. Star Force divides its roughly sixty ships, destroys the attackers, and learns the cost of allowing one to reach the surface. A Macro strike destroys Hilo, while another vessel deploys ground machines and processing installations in South America before the fleet can eliminate it. Attempts to attack these ground forces from orbit incur unacceptable losses. The human-commanded vessels can now win limited battles in space, but the invasion has shifted to Earth, where Macro ground forces and processing systems are established in South America. Star Force cannot sustain orbital attacks against those deployments.

The South American invasion grows while Star Force's first diplomatic effort collapses. An intruder murders Pierre aboard Versailles, seizes his ship, and resumes lethal civilian testing. Kyle accepts Nano injections so he can leave Alamo, gaining exceptional strength, speed, durability, and a direct mental link with Nano structures. He infiltrates Versailles, defeats the hijacker, and survives her gunfire, but she kills herself rather than identify any sponsors. The ship is recovered, while possible official involvement remains unproved. Crow makes the enhanced Kyle responsible for future diplomacy because he is much harder to assassinate. Kyle also learns that Alamo can fabricate technology and may be able to reproduce its manufacturing systems if supplied with scarce materials. He produces a small laser weapon and cautiously reopens contact with the United States senator. During a guarded meeting, Kyle offers the prototype and requests recognition, a supplied base, recruitment access, funding, and an alliance. The senator cannot grant these terms herself but agrees to pursue them. Cooperation has become urgent: Macro forces are spreading north through South America, their domes are producing more machines, and their defenses have reduced the effectiveness of nuclear weapons and artillery.

Star Force receives an evacuated Andros Island as its base. Kyle builds concealed fabrication facilities, expands portable laser production, and plans for independent ship construction. He then joins a United States Marine deployment in the Amazon, where General Kerr uses tactical nuclear mines and helicopter decoys to draw Macro machines into an ambush. The first close engagement devastates Kyle's platoon. Nano protection keeps him alive despite a ruined arm, and concentrated laser fire forces one Macro to retreat, but the ordinary troops suffer catastrophic losses. Alamo extracts Kyle and the last sergeant fighting beside him, Lionel Wilson, then regrows Kyle's arm. Kyle proposes a volunteer ground force whose members will receive Nano alterations and carry far heavier weapons. Kerr and Crow ultimately authorize the plan. Kyle also draws limited information from Alamo about the Nanos' creators: they are biological, live beyond the Solar System, and appear connected to a gas giant, though his conclusions remain uncertain. On Andros Island, the first multinational group of combat veterans accepts enhancement. Wilson becomes the senior enlisted leader. Sergei Radovich and Kwon distinguish themselves among the recruits, and Kwon demonstrates that he can handle the new reactor-powered laser pack even before treatment. Star Force now has the beginnings of a ground arm designed specifically to fight Macros.

Kyle deploys nearly six thousand Nano-enhanced Marines to Buenos Aires and sends six groups toward Macro domes. The altered troops destroy seven attacking combat machines quickly, proving the new force's basic concept, but long-range missiles prevent them from remaining concentrated. At the first dome, concealed worker machines inflict heavy casualties, and the shield resists massed laser fire. Kyle's force is flanked as the initial assault companies are destroyed. With another missile strike possible, he orders a direct advance through the shield. Inside, the dome proves to be a factory. Their weapons damage it but cannot finish it. Lionel Wilson volunteers to stay behind and detonate his reactor pack in the factory intake. The explosion destroys the installation, but Wilson is missing afterward. The success costs most of Kyle's battle group, leaving only two of ten companies intact enough to emerge. Kyle is badly wounded but continues commanding. The Marines have discovered that the shield blocks signals and energy weapons while allowing a slow physical entry, and they now know how a dome can be destroyed from within. The price of that knowledge shows that eliminating the remaining factories will demand extreme losses unless Star Force finds a safer method.

After the first factory's destruction, other Marine groups eliminate two more domes at severe cost. Kyle remains with wounded survivors while Radovich leads the mobile troops onward, but that entire force is later ambushed and lost. Tunneling Macro workers attack Kyle's position. Alamo conducts a dangerous extraction, saving sixteen people, including Kwon, whose Nanos are regrowing part of his missing foot. With three domes left and signs of a much larger Macro presence near Venus, Kyle combines recovering veterans, new enhanced recruits, conventional troops, artillery, and ships used for missile defense. Nuclear artillery defeats a major Macro charge. One remaining dome then destroys itself, killing six inexperienced companies, while another is breached and destroyed from a distance by repeated nuclear strikes. More than five hundred Macro contacts launch a final surprise attack with their shields inactive to avoid early detection. A machine overturns Kyle's mobile headquarters, killing much of its conventional staff, but Kyle and Kwon escape and destroy it. The combined human force wins the wider battle while losing nearly a third of its personnel. The last dome self-destructs. Earth's active ground invasion is over, although the Macro force gathering near Venus makes clear that the larger war may continue.

Kyle returns to Andros Island and resumes his relationship with Sandra, with marriage now under discussion. Star Force expands its factories, fleet, and standing force. Crow remains nominal head and controls the fleet, while Kyle keeps a senior combat role with the Marines. The organization also retains captured survivors of an earlier species for possible restoration and communication. Its victory on Earth does not bring lasting security. A vastly larger Macro fleet appears near Venus, including new combat ships and major invasion vessels. Star Force launches nearly eight hundred ships but is badly outnumbered. Instead of attacking immediately, the Macros transmit a repeated signal. Kyle uses Alamo's records to establish rudimentary communication and speaks for Earth's resistance. The Macros demand control of the Solar System and threaten humanity with removal. Kyle argues that human ground forces are superior, prompting a different offer: the fleet will withdraw if Earth supplies a cargo vessel filled with troops. He negotiates a one-year deployment, after which those soldiers are to return and be replaced by another full army. The Macros accept and withdraw. Earth gains one year without invasion, but only by accepting compulsory military tribute for an unknown external war. Kyle decides that when the transport returns, he will lead the first contingent rather than send others without him.

Earth has eliminated the active Macro ground force, but the wider conflict remains unresolved. Star Force rebuilds on Andros Island, expands its ships and factories, and develops a large standing force of Nano-enhanced Marines. Crow remains the organization's nominal leader and fleet commander, while Kyle Riggs retains a senior combat role over its ground forces. Kwon survives in Riggs's command element, and Riggs resumes his relationship with Sandra as they consider marriage. Wilson is missing and presumed dead after destroying a Macro factory, while Radovich and his force are lost in an ambush. A much larger Macro fleet then arrives near Venus. Unable to win a direct battle, Riggs negotiates a one-year reprieve by agreeing that Earth will provide a shipload of Star Force ground troops for service in an unknown external war, followed by a replacement army. The Macros withdraw, but the arrangement is coerced tribute rather than peace. Riggs commits to accompany the first contingent himself. The identity and aims of the Nanos' biological creators, the larger Macro war, and the political background to Pierre's murder remain open.