The Sun is dying and a group of Earth's citizens have been sent on a journey through space to deliver a stellar bomb that is supposed to recapture the once-brilliant sunshine. The men and women of the Icarus II are confronted with the opportunity to rendezvous with the previous Icarus mission, deviating from their original plan. The decision is placed on the astronaut in charge of payload, Robert Capa (Cillian Murphy), who decides that with the recovered Icarus I payload, they have twice the chance of success. Not everyone agrees, notably the engineer, Mace (Chris Evans), who holds resentment toward Capa for the duration of the mission. The mission goes awry and the crew is put in jeopardy when the spacecraft's sunshield is damaged due to the change in course to recover the Icarus I payload. Despite the increasing difficulty of their mission, the crew continues to push themselves and eachother to complete the mission and restart the sun for the benefit of future Earth generations.