Before they attack, a strange Klingon appears and fires on one of the group. Alexander runs to safety, and after a brief struggle, the remaining assailants flee. The stranger calls himself K'mtar, a close friend of Worf's family who has been sent to protect them. Markings on a dagger left at the scene then indicate that the would-be assassins were sent by the Duras sisters, a rival Klingon family that may be attempting to take Worf's brother's Council seat. Later, K'mtar questions Worf about the wisdom of raising Alexander far from Klingon culture. Worf confesses that his son shows little interest in becoming a warrior, and K'mtar offers to help. He visits Alexander in his room at bedtime, where the boy admits how frightened he was that Worf would be killed. K'mtar reassures Alexander that if he trains to become a warrior, he will someday be strong enough to protect his father.

Worf and K'mtar begin to teach Alexander to fight by recreating the previous day's assault in the Holodeck. Alexander holds his own at first, but backs off when he has a chance to kill one of the assailants. K'mtar angrily berates him, and the boy runs off. Later, K'mtar privately tells Worf that he thinks Alexander should be sent away to a Klingon training academy. When Worf refuses, K'mtar threatens to invoke ya'nora kor, a bid to take custody of Alexander away from Worf.

Worf asks Troi's advice, and she tells him that Alexander's human side is just as important as his Klingon heritage. Soon afterward, Riker and the crew locate the Duras sisters and demand that they board the U.S.S. Enterprise. The sisters are enraged when they are accused of trying to assassinate Worf, and prove this fact when they point out that one of the markings on the dagger is a symbol for a child who hasn't even been born yet. Worf, hoping K'mtar can explain, is shocked to find him in Alexander's room preparing to kill the boy. Furious, Worf attacks him, after which K'mtar reveals that he is Alexander, and has come from the future.

K'mtar explains that he grew up to be a diplomat instead of a warrior, and became the catalyst for Worf's murder 40 years later. Beside himself with grief, he decided to transport back in time and either change Alexander's ways or kill him. Realizing this really is his son, Worf is overcome with pride, and tells him the only way he can die an honorable death is knowing he allowed Alexander to accept his own destiny. The two embrace, and K'mtar leaves. Later, Worf approaches young Alexander with a new attitude, ready to let his son be who he wants.