Gravely injured in a Lenarian attack, Picard slips into a white, seamless limbo while Beverly struggles to save his life. There, he encounters Q, who informs Picard that he is dead and this is the afterlife — and that Q himself is God! Picard refuses to believe that he is dead, let alone that Q is the supreme being. But Q is determined to prove otherwise. He produces the artificial heart that failed Picard and caused his death, which triggers Picard's sense of regret. With Q's urging, he admits that, given the opportunity to live life over, he would do things differently.
Picard's wish is Q's command. He is suddenly a young ensign of 21 and Q gives him the opportunity to relive and avoid the fight that led to his being stabbed through the heart. If he succeeds, he will return to the present with his real heart intact, and the galaxy's history will remain unchanged. If not, he will die in that present and spend eternity with Q.
Initially, Picard was stabbed when he rigged a gambling table to help his Starfleet friend Corey get revenge against a Nausicaan who cheated him. Since he must avoid that conflict, he attempts to talk Corey out of gambling in the first place. Corey plays anyway, the Nausicaan cheats him and wins, and Corey naturally asks Picard to help him get revenge. But Picard refuses, backed up by a another friend named Marta, and a furious Corey storms off.
Further changing his past behavior, Picard spends the night with Marta. But in the morning, she worries that they have ruined their friendship. When Picard, Marta and Corey get together that night, the tension between the three of them is palpable. Then things get worse. Three Nausicaans appear and taunt the group, hoping to provoke a fight. Picard sees the Nausicaans prepare to draw their weapons and quickly knocks Corey to the floor in order to prevent the fight from occurring. But since Corey and Marta can't understand Picard's actions, they see them as a betrayal and walk away in disgust, announcing to Picard that they are no longer friends. Q congratulates Picard for changing his destiny, and he is thrown back into the present time. However, he has returned to the U.S.S. Enterprise as a lieutenant, junior grade.
According to Q, everything is as it should be — the changes in Picard's present reflect the changes he made in his youth. But Picard is unable to go about his business as a lowly astrophysics officer. Disoriented by the lack of respect he encounters at the hands of his former subordinates, he speaks to Troi and Riker about his chances for advancement, and is crushed to hear that while he is a good, reliable officer, he just doesn't stand out. Desperate, Picard summons Q and begs that he would rather die than live any longer as an average, dreary man. Q obliges and the dreaded fight ensues. However, at the moment he is stabbed through the heart, Picard wakes up in Sickbay in the present time, surrounded by a very relieved Beverly, Worf and Riker. Despite the traumatic ordeal, Picard realizes that he feels grateful toward Q, who gave him a chance to understand why he is the man he is today.