Picard summons Wesley Crusher to the Bridge, where he informs the youngster that he has been accepted to Starfleet Academy. He further honors Wesley by asking him to accompany him on a final mission to help mediate a dispute on Pentarus V. When the U.S.S. Enterprise is called to investigate another nearby crisis, Picard and Wesley proceed alone, traveling with a representative of the planet, Dirgo, in his dilapidated shuttle. En route, the shuttle fails, forcing an emergency landing on a desert-like moon. Upon learning Dirgo is not traveling with water, Picard positions a makeshift arrow in the sand to indicate their direction and heads toward a mountain range for shelter.
Back on board the U.S.S. Enterprise, the crew learns that the shuttle is missing, but cannot aid in the search because they are involved in an emergency mission of their own, removing an ancient waste vessel that is leaking radiation from the atmosphere of a nearby planet. Meanwhile, Picard, Wesley and Dirgo reach the mountains, where Wesley locates a water fountain inside a cavern. Upon discovering a force field that stands between them and the water, an impatient Dirgo begins firing at the force field, summoning an electrical sentry that begins moving toward them. Dirgo fires at the sentry, triggering a rock slide. As the boulders hurl toward Wesley, Picard pushes him out of the way, and is severely injured in the process.
While Picard's condition worsens, Dirgo bullies Wesley into trying to distract the sentry by setting his weapon to fire automatically, allowing Dirgo to shoot through the force field to try to reach the water. The plan seems to work, until the sentry splits itself in two, enveloping Wesley's weapon and killing Dirgo.
Riker and the crew aboard the U.S.S. Enterprise conclude their mission and join the search for the shuttle. But as the cold night falls on the desert moon where he and Wesley are trapped, Picard grows weaker. Wesley tries to keep his captain alive by expressing his affection for the dying man.
As Picard struggles to hold on, Wesley devises a plan to foil the sentry. He shoots his phaser to lure the electronic guard, then tries to disengage it with a tricorder. Eventually, the sentry passes right through him, releasing the force field and giving Wesley access to the water, which he rushes to Picard. Soon afterward, an Away Team from the U.S.S. Enterprise rescues them, and Picard credits Wesley for saving his life.