Mar-Vell of the Kree, known on Earth as Captain Marvel, dictates a journal of his life into a recorder: originally dispatched to Earth to spy it out for possible conquest, he instead rebelled against his people and became our world’s protector. Now, with Mentor, ruler of Titan, and his son Eros (Starfox), Mar-Vell is heading for the ark of Thanos. They seek the body of Mentor’s other son, so that the would-be galactic conqueror can be entombed on his homeworld. They arrive and as they stand before the petrified Thanos, they are attacked by an army of diverse aliens who worship Thanos as a god and await his resurrection. Mar-Vell and the group win the fray with a minimum of violence and Mentor orders them to forget his evil son. As the Titan party departs with Thanos’ body, Mar-Vell falls ill; a medical scan back on the ship reveals the grim news: Mar-Vell is dying of cancer. It was caused by exposure to a powerful nerve gas years earlier; he is resigned to his fate and informs his beloved Elysius.
Mar-Vell resumes his journal, relating his exile to the Negative Zone, his merging with Rick Jones, his adventures with the Avengers, and their final battle with Thanos. He returns to New York to locate Rick and inform his old friend about his condition, and warn him about the possibility that his health may be endangered too. When Rick learns that Mar-Vell is resigned to his fate, he reacts with anger, determined to help his former partner. Rick approaches the Avengers and appeals to them to devote themselves to finding a cure for cancer. When the heroes give a guarded response, Rick angrily storms out.
The news that Captain Marvel is dying spreads throughout Earth and the universe, exciting joy among his enemies but shock and sorrow among his legion of friends. Mar-Vell is concerned about Elysius, a former enemy turned lover, and reacts with anger over his impending demise. The Avengers discover that Mar-Vell’s Nega-Bands, which have kept him alive thus far, are also preventing a cure. Then the former Kree warrior collapses and is confined to his bed. From all over the galaxy, friends and enemies come to pay their respects to the fallen hero. Some try to comfort him, others honor him, Spider-Man walks out, unable to deal with his emotions. Soon, Rick Jones appears, to apologize to his old friend and spend some time with him. Later, Drax and Moondragon bring an unexpected visitor: General Zedrao of the Skrull Empire. He has come to present the medal of valor to his people’s greatest enemy as a tribute to his courage. Mar-Vell is not unaware of the irony that his own people have not so honored him.
That night, word comes that Mar-Vell has fallen into a coma. The visitors gather around his bedside with Mentor pronouncing his death unfair. As the word "unfair" echoes through the room…Mar-Vell is awakened from his solitary bed by a revived Thanos, who restores him to health with a gesture, even clothing him in his familiar uniform. Thanos announces he has returned for one last magnificent battle with his old foe. On a pathway beneath the enormous heart of his universe, the Titan villain acts to destroy the heart and the Kree hero seeks to stop him. Mar-Vell finds himself fighting the ghost of his dead enemies, joined by Thanos, to force him to accept their reality: the inevitability of death. When Mar-Vell finally accepts his imminent passing, Lady Death approaches, takes both Mar-Vell and Thanos by the hands, and as the giant heart ceases to beat, leads them off on their next journey….
Back in the room, the EKG goes flat and Mentor pronounces, "He’s gone."