"'Horizon" is the 20th season-two episode of Enterprise. It originally aired on April 16, 2003.
Enterprise makes a rendezvous with Ensign Mayweather's family's cargo ship for a short visit while the Enterprise takes a trip to a planet under heavy volcanic activity.
At the direction of Starfleet, Enterprise makes a 30 light-year detour to a planet passing between two gas planets.The gravitational forces on the planet are going to cause heavy volcanic activity and the Enterprise detours to see it happen first-hand.
Ensign Mayweather realizes the Enterprise will be crossing paths with his family's cargo ship and makes a personal request to Captain Archer to take leave to visit them.