The episode serves to provide character development of CaptainJean-Luc Picard, who is featured in this episode to the general exclusion of the rest of the cast. Its primary theme is the effect on the present of changing the past.
During a diplomatic mission, Captain Picard is shot in the chest by a group of radicals. As he slips into unconsciousness, he finds himself in an unearthly realm where he is greeted by the god-like alien Q, who bluntly informs him that he is dead and in the afterlife.
Q explains to Picard that the energy blast he took shorted out his artificial heart and that a natural heart would have survived. Picard lost his original heart years ago when he was stabbed through the chest during a bar brawl with some Nausicaans, a race of quick-tempered and aggressive aliens. Picard's regret over his "wild youth" led him to become the serious and disciplined man he is today.
Q offers to let Picard go back in time to prevent himself from being stabbed. Q assures him that any changes he makes to the timeline will not affect anyone other than him. He is sent back to two days before the injury, meeting with his friends and fellow cadets Corey Zweller and Marta Batanides. His "newly changed" personality comes as somewhat of an unpleasant surprise, and he alienates his friends. The person they knew as fun-loving and quick to anger is now staid, slow to anger, and often unintentionally insulting.
Events proceed as they did with Zweller becoming enraged with a group of Nausicaans who cheat him at dom-jot. Picard blocks Zweller's plan to cheat them back by rigging the dom-jot table, angering his best friend. The next day the Nausicaans taunt Picard and his friends. Instead of taking on the Nausicaans, Picard throws Zweller out of the way of the fight. The Nausicaans call them cowards and leave, as do Zweller and Batanides. By refusing to stand up for Zweller, Picard has lost his friends but saved his heart. Q returns Picard to the present.
Picard finds himself on the Enterprise as a junior lieutenant in the astrophysics department. Q tells him that, as a consequence of the changes to his past, he has led an unremarkable career doing routine work. Picard consults with Riker and Troi on the possibility of him moving on to higher positions. While they consider Picard a competent and hardworking officer, his aversion to risk means he never distinguishes himself.
Picard confronts Q, who tells him that although the bout with the Nausicaan nearly cost him his life, it also gave him a sense of his mortality. It taught him that life was too precious to squander by playing it safe. Picard realizes that his attempts to suppress and ignore the consequences of his indiscretions have resulted in him losing a part of himself. Picard then declares that he would rather die as captain of the Enterprise than live as a nobody. Q sends him back to the bar fight and events unfold as they did originally, with Picard being stabbed through the heart and laughing as he collapses to the floor. In the present, Picard awakens in sickbay, a captain again.
As Picard recovers from his injury, he wonders whether he really journeyed into the past or whether it was merely a hallucination or one of Q's tricks. In any case, he is grateful for the insight the experience gave him.