The fourth season of Mariner saw major changes in the production end, which in turn resulted in a virtual re-invention of the series. Rhoberth Fox, creator and executive producer of the show, left the staff after "creative differences" with the North American League Broadcasting Company executives.
Taking over at the helm of the program was veteran television producer Fred Larson, Jr. who has previously run such programs as SUPER-COPS and an updated version of Juliette Verne's A YEAR BENEATH THE WAVES (retitled YEARS BENEATH THE WAVES) for Saturday mornings, as well as the very popular THREE'S THE CHARM about a trio of sisters who are also practitioners of magic. He sought to "revitalize" the series, which amounted almost to a re-invention. One result of the changes he instituted was a delayed production schedule.
Characters dropped from the series (assumed dead) included Tophora, Sarukai, Shyanna and Vulia.
Mariner's fourth season, with teasers:
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- On The Other Side: The damaged Mariner approaches a dead planet in the "Mystery Zone" of the Antilles Cluster. There, the crew finds the remnants of the Far Voyager one of her sister ships. Salvaging parts lets them repair the ship, but they also meet the new regular Lance Quick and his dog Rascal. With his help, Professor Gideon and Septa are able to track down the beacons of various escape pods containing the missing officers.
- Slave Planet: Gorgul VII is a planet that trades in slave labor, and it is here Captain Klausfelder and Stavros are in hiding. Ultimately, the Captain romances the leader of the rebel slaves into helping them escape. It turns out a humanoid race called Medusoids are the reason this region is called the Mystery Zone--they hunt down anyone encroaching on "their" space." The Mariner arrives to rescue the Captain and Stavros. Now they start searching for Magnus.
- End of the Rainbow: Tracing Magnus' escape pod, the Mariner comes across a strange world whose human natives live in fear of a race of tiny green bearded men who hoard gold and are forever smoking pipes, full of psychic powers that seem like magic. It turns out the "native" were kidnapped from Ireland a thousand years ago, and the tiny green men are the origin for legends of leprecauns.
- Only Human: An orbital manufacturing plant is where they find Magnus. He is being used as a template to create a new line of androids to finish construction of a terrible weapon, one that can cause stars to go supernova. Our heroes escape capture and rig an explosion which destroys the orbital plant, while Magnus' body is wrecked. They gather parts from the debris so Lance can rebuild a body for him. His head at this point is intact and can still speak.
- Under The Microscope: While Magnus is being re-assembled, invisible aliens board the Mariner in an effort to perform psychological experiments on the crew. Among other things, they hope to learn the meaning of words like "friendship" and "loyalty." When Rascal seems to sacrifice himself for Lance and the others, the aliens believe they understand and save the crew.
- Far From Home: The crew goes on trial for murder after picking fruit on a world where the intelligent life are all plants, brought before a great Forest Tribunal. Magnus must act as counsel for the defense while the others plot their escape from the deadly Root Warriors.
- The Gemini Hour: A rift in space reveals a life pod identical to those of Mariner, carrying evil versions of Fiver and Stavros from an anti-matter universe where their mission to the Antilles Cluster has been one of conquest.
- Children's Eyes: While Captain Klausfelder tries to negotiate between the leaders of two rival factions in a system, Lance befriends the young princess at the center of the conflict. In the end, the two children manage to get the vying armies to disarm.
- One of Our Moons Is Missing: Stavros is charged with stealing one of thirty seven tiny moons in orbit around a world whose natives live at a bronze age level, save for the royal family who have space ships and ray guns. Magnus and Lance, working with the Captain who seduces a princess and thus proves the moon was destroyed by one of the royal family's weapons.
- The Sleep of Reason: At ancient ruins on world that suffered some strange catastrophe, the Captain meets a sad and beautiful alien. It turns out her people meddled with their cycles of hibernation, releasing monsters from their unconscious. He needs to wake up and then make sure no one falls asleep anywhere near this planet, lest the monsters return and destroy the ship.
- The Mirror War: On a ice-bound world, the Medusoids are threatening a population consisting entirely of clones--a dying race as "copy errors" build up with each generation. The Clones try to kidnap the crew of Mariner long enough to make copies, but the Clones help their progenitors escape. As our heroes flee, a fleet of Medusoid warships approach the ice-world.
- Beware The Moon: Fleeing a Medusoid battle group, the Mariner finds the ships won't approach one particular world where the inhabitants (also Medusoids) live in a Bronze Age. They welcome Lance, Magnus, Fiver and Stavros, while Captain Klausfelder befriends the local Moon Priestess. Then, night falls and the natives begin to turn into wendigos. Worse, so do the humans! Magnus has to get everyone back to the ship and way from the influence of this planet's strange moon, made of exotic particles.
- Tick-Tock: Lance and Rascal seem to be the only ones unaffected by a strange cloud through which the ship travels, one that slows down all the adults until they seem to be frozen in place. It is up to Lance to somehow solve the mystery before they are all stuck forever in a kind of "Sargasso Sea" in space!
- Sky Pirates: The Mariner is captured by the most notorious band of space pirates in known space. The only thing that can save them is if the Captain can persuade the Pirate Leader's daughter Virginia to help them escape.
- A Question of Scale: After the ship comes to a strange world roughly at the level of XXth century Earth, a team is sent down and discovers that everything on this planet is of gigantic size. They themselves are seized by a child, who believes them to be toys! But Lance manages to persuade the little girl to let her new friends go.
- Bad For A Bone: What seems to be nothing but a fruit hatchs a monster than devours bones. The whole crew is in danger and must hunt the shape-shifting creature down before it kills and eats them all.
- Mirror, Mirror In Deep Space: The Mariner finds itself affected by a strange artifact, one that seemingly makes some people into wraith-like beings unperceived by others until Magnus can undo the damage, mostly because Lance can still somehow sense Rascal's presence. Separation makes the heart grow fonder, resulting that Fiver and Stavros finally agree to marry.
- Toyworld: A barren landscape on a distant planet is actually the workshop of an insane Medusoid exile who has used Eldren technology to create fantastic (and fantastically dangerous) toys. He uses Magnus as a template to create doubles of the crew in an effort to take over the ship and escape his prison.
- Fiver's Brain: A group of bronze age humanoids worship the fragments of an ancient Eldren library. One of them follows instructions to remove Fiver's brain in order to make the mainframe computer work. The crew has to race against time to find the brain and re-insert it into her skull.
- Zone of Glass: Stavros is given a gift by an alien princess after the Mariner goes through her father's system. Said gift is a bejeweled mirror that turns out to be a portal to another dimension, where Lance falls in and finds the Princess' twin sister, who has remained a child since becoming trapped here.
- Third Star From the Left: An angelic Medusoid hijacks the ship for the sake of a mysterious quest, as time and space seem to collapse around everyone. It falls to Lance to solve the final riddle amid the ruins of an ancient planet, and in doing so makes Magnus into a flesh-and-blood human being.
- Through A Glass, Lightly: Lance wakes up in a nice home back on Earth, with Fiver and Stavros as his parents. They slowly come to the realization they are trapped in a virtual reality machine, and eventually break free with the help of a young woman named Wulee. Her father is the Caretaker of a colony of Eldren who have lost their technology in the wake of a terrible conflict ages ago. The Mariner has been destroyed in an ion storm and the survivors came to this planet in escape pods, where the Caretaker put them into the VR to keep them quiet yet learn about them. The still-free Magnus and Klausfelder stir up the natives to overthrow the Caretaker (who has been using VR to cloud everyone's minds). Magnus and Wulee become a couple, while all of them settle on the planet to build new lives for themselves.
Critical and audience reaction to the fourth season was almost universally negative. The program's ratings dropped steadily, which led to the show's cancellation. A lawsuit from the Roddenberry estate is currently in litigation to prevent the entire season from entering syndication. It is expected to win.