Seaview encounters a sunken WWI sub...with someone still left aboard.

Seaview is investigating a thousand-mile wide communication blackout. The source of this is a large alien brain found under the sea. It is broght aboard and takes over visiting scientist, Dr. Lindsay. With his help, and after possessing Captain Crane, the alien vows to take over the Seaview and after that, the Earth.

Two scientists examining a radioactive volcano are attacked by a wolf. One dies, and the survivor is infected by a virus that causes him to change from man to werewolf and back again. Admiral Nelson is exposed to the virus and the crew must find a vaccine.

As Admiral Nelson demonstrates a new tracking device for a visiting U.S. senator, it seems to show that Seaview is the only life left on earth.

Captain Crane searches for a lost diving bell containing Admiral Nelson, Chief Sharkey, and Dr. Sprague.

Seaview is investigating a UFO. Along the way, they pick up a shipwrecked old man -- almost always a bad omen when our gallant crew finds a castaway! The bedraggled fellow has a sack full of strange, frightening toys capable of murder, and of destroying the submarine. Turns out the alien ship needs to melt down Seaview's hull for fuel. Nelson and Crane do their best to foil the aliens' plans before it is too late.

A UFO crashes and an alien assumes the form of Admiral Nelson.

Captain Crane rescues a diver from a wrecked atomic sub. He turns out to be Kowalski's brother, Stan, a Navy diving specialist. When the Seaview needs his help in getting off the ocean floor, Stan is not up to the job.

Bainbridge Wells is filming a segment of his "Science On The Move" television series on a small island off the coast of Chile. A sea creature comes ashore and kills his crew. Wells convinces Admiral Nelson to return to the island because he wants to prove that the creature really exists. Crewman Patterson has a special interest in the mission.

Admiral Nelson and Captain Crane are involved in a mind-control experiment, with Chief Sharkey caught in the middle.

Faceless aliens invade Earth and try to take over an underwater atomic base. The leader takes the form of an old, deseased friend of Admiral Nelson in order to convice Nelson they mean no harm. Nelson will have none of it and leads a landing party to the base to stop the aliens, even if the cost includes their own lives.

A ghostly ancestor of Admiral Nelson visits him aboard Seaview.

Twin scientists - one good, one evil - come aboard Seaview. The evil twin is out to create a radioactive "plant man."

Seaview and an enemy sub battle to recover a superbomb from the ocean floor.

While racing to help a foundering research vessel, the Seaview's nuclear reactor goes critical. Admiral Nelson's right hand is exposed to intense radiation as he fixes the problem, causing a flare-up of the "werewolf" virus that he carries.

The Seaview is called in to help track an artificially created life form, now loose in the Pacific. The creature, which is growing at a fantastic rate, has its own agenda -- starting with a takeover of the crew.

As World War II draws to a close, a secret underwater Nazi base is damaged during a sea battle. A Nazi scientist and his aide are accidently put in suspended animation. Thirty-five years later, the crew of the Seaview discovers and revives them. The Nazis attempt to carry out their interrupted mission: destroy the capital cities of the Allies.

Arctic Listening Station XZ-5 receives a message from a voice from space (""laser beeeeeam""). Professor Bergstrom, ignoring the advice of his assistant, activates their beam and brings the alien, living flame, to Earth. Now, this Heat Monster wants the Seaview to detonate a bomb under the polar ice cap. How can the intrepid crew defeat this new menace?

The crew of a lost submarine returns as rock men to menace the Seaview. A new man, Kowalski's friend Richards, is captured on a diving mission and turned into a Fossil Man. Nelson is then ordered to turn command of the Seaview over to these rock men. Will Nelson comply? Will the crew be dipped into the transformation lava to exist as living rock?

As the Seaview conducts a marine census, Captain Crane spots a mermaid. He brings her aboard and falls under her spell. A sea creature follows the mermaid and proceeds to cause big trouble on the sub. The problems are compounded when the Seaview is ordered to disarm a nuclear device that has been planted off the coast of California.

The Seaview is on a top secret mission to transport a 3,000 year old sarcophagus from New York to a country in the Middle East. The United States hopes that by returning a national treasure, war will be prevented. The inhabitant of the sarcophagus has other ideas, and attempts to prevent the Seaview from reaching her destinaton.

The Seaview takes on a skeleton crew and is being used to guide a new interstellar space probe. However, Chip Morton is taken over by an alien shadow man which wants to stop the probe.

While searching the deep for an enemy complex, the Seaview is rammed by another sub. The crew rushes to make repairs before the air runs out and a lurking monster swallows a diving party led by Crane.

While Nelson and Sharkey search by air for an uncharted island, Seaview brings aboard a gigantic egg from the bottom of the sea during a routine specimen collection. It later hatches a fully grown, orange creature which kills a background guy and tosses Kowalski around the missle room. Nelson returns and (in a very un-urgent manner) has the crew hunt down this grunting thing as it terrorizes the crew. Later, Crane and Kowalski take the flying sub out to investigate the area, crash landing near the uncharted island. Another orange crature (one that speaks and is the leader) captures them and brings them to creature HQ. The monsters are aliens from Scorpious which are trying to hatch millions of eggs. Can the crew stop this invasion before these amphibian aliens take of the Earth?

The Seaview is carrying Atlantanean statues in its missile room as a favor for the State Department. As they wait for Captain Crane to return, a midget clown emerges from one of the crates and begins sending forth his animated waxwork duplicates of the crew. Crane's only hope is to try to revive Admiral Nelson and retake the ship. But, can they?

A mysterious cloud is enveloping the Earth and causing massive Tsunami and other catastrophic environmental damage. Crane takes the flying sub in to find out the cause and is taken over by an evil alien. Once aboard, this alien tries to stop Nelson before he can destroy the cloud with nuclear weapons.

Admiral Nelson has been brainwashed. After getting a vital energy source, he attempts to kill Crane and the visiting Dr. Land in an undersea cave. He then returns to the sub, gasses the crew and sets the reactor to blow. Can Crane recover and return to the Seaview before Nelson can destroy it?

The Seaview is being buffeted about by underwater explosions due to the eruption of an active volcano. Dr. Turner (Victor Jory) is aboard to stop the eruptions. However, his true mission is to bring up ""elixir stones."" An alchemist, Turner needs the stones to keep him immortal. However, in order to bring up the stones, he needs to stimulate the volcano into full eruption!

The Seaview crew is being entertained by puppet cairactures of the Captain and Admiral, compliments of Professor Multiple. Multiple remains on-board when the sub departs, and his dolls soon come to life, replacing their real-life counterparts. Only Nelson and Crane avoid capture and transformation. Multiple boasts that he and the others are all puppets, created by machines from the future that have traveled into the present, and need the Seaview as a new host body. Can Nelson and Crane overcome this fantastic threat?

"Those who see the Flying Dutchman never, never reach the shore." Investigating the loss of Navy ships, Nelson finds an ancient dagger in a cave on an uncharted island, and falls under a strange curse. Haunted by visions of skeletons and an anachronistic ship, he has trouble convincing the crew of his sanity. Meanwhile, Seaview is sailing in circles, and the visiting Commander Van Wyck seems to have disappeared. Guest star Warren Stevens also appeared in "The Saboteur" and "Deadly Invasion".

Aliens snatch a manned space probe launched from Seaview with Chip Morton aboard, and transport it at the speed of light to their observation post on the rocky, unstable surface of Venus. Checking out the duplicate capsule, Crane suffers the same fate before he even has time to launch. With Chip blinded and a prisoner, and the planet's surface due to undergo catastrophic quakes in a few hours, the odds seem to be against the two men.

"There's nothing to do here but to keep from disappearing." Lt. Commander Morton Seaview is carrying a new missile, and Nelson has orders to deliver it to its launch site at all costs. Unfortunately, the missile malfunctions, and Nelson can't get into the sealed silo to fix it. Soon, the crew starts to disappear, and bizarre phenomena plague the ones who remain.

In an attempt to control the planet's tides, Dr. Randolph Mason (a nut if ever there was one -- he is part scientist, part make-up artist!) has invented a powerful electromagnet and established a magnetic field around the moon. The only person who seems to recognize the obvious danger in this silly plan is Harriman Nelson. At first glance, it would appear that Nelson has killed Dr. Randolph. At second glance, it would appear that Captain Crane has betrayed the Admiral. On third glance, the moon is getting closer and closer to Earth, and will soon collide with our beautiful blue orb -- unless the Seaview can save the world. Again. * In this episode, we learn that Chief Sharkey attended Lincoln High in Coney Island, Brooklyn, New York. (There actually is a Lincoln High in Coney Island.

Doctor Blanchard has created a device to control the actions of a white gorilla. Unfortunately, his assistant Leo Brock wants the fame that the inventor of such a device would gain. As a result he uses the device to enrage the gorilla and kill Blanchard. Nelson gets there too late to save Blanchard, but the gorilla is taken on board. Brock sets the gorilla free and he runs amock until both Brock and the gorilla are killed.

A man from the future sends two androids back in time to kidnap Nelson from Seaview in order to add him to a collection of other famous military figures abducted from various eras of the past. The plot of this episode is virtually identical to the plot of the ""Time Tunnel"" episode entitled ""The Kidnappers"".

Seaview is on the lookout for an enemy sub and its underwater sub-pen. Sonar picks up a contact. The rogue sub fires at Seaview, which is saved only by virtue of her new electronic hull shield. Not so fortunate is Captain Crane, who has just located the sub-pen while on patrol in the FS-1. A powerful laser fires a beam at the Flying Sub, crippling the ship. Running out of air, moving in and out of consciousness, Crane is unable to give the pen's coordinates to Nelson. Thanks to the hard work of some enemy agents aboard, Seaview seems unable to rescue the Captain. Worried about Crane trapped in the Flying Sub, Admiral Nelson is particularly impatient in this episode. He constantly barks at Morton and the Chief.

A scientist experimenting with plant life on a remote island has run into trouble. A shore party from Seaview arrives only in time to hear his dying warning that the world will be taken over in eight hours. Nelson brings aboard the only unusual thing he can find -- a red orchid, which proves to be a malign alien (that proceeds to take over his mind and those of the crew).

finds herself suddenly out of touch with the rest of the world, in the wrong part of the ocean and encountering strange creatures. It seems she's been thrown a million years back in time. Then the Admiral opens his cabin door and finds himself back in his Santa Barbara office, confronting the strange Mr. Pem and his pocket-sized time machine, and has to play a risky game before time can return to its normal course. The early part of this episode contains two astronomical errors. First, Nelson takes snapshots of the eclipse-darkened sky with an ordinary camera, but when the shots are developed they show galaxies and nebulae that could only be seen with a telescope. Second, the Admiral describes the pictures as showing 'constellations'. Henry Jones (Pem) also appears as Sprague in "Night of Terror" and once again as Pem in "No Way Back". This episode features re-used footage from "Thing from Inner Space".

The Seaview is en route to rendezvous with the fleet when Sharkey reports a missle fuel leak. Crane and Morton believe it's worth returing to port to repair, however Nelson knows how to handle it. Taking a small breathing device with him, the Admiral locks himself in the compartment in question to effect repairs. However, he drops a wrench, the circuts blow and Nelson is knocked out. When he comes to, he's gripped by paranoia which worsens with each passing minute. Trusting no one, Nelson loses his grip on reality, arresting Doc, fighting with Sharkey and finally launching a nuclear missle at the fleet!

Seaview has been sent to the ocean floor by mysterious pressure impacts. Crane, Sharkey, and Kowalski go out in the Flying Sub to investigate. They, too, are sent to the bottom of the sea. Strange creatures (half men-half fish) present themselves and explain that they intend to take over Seaview (who doesn't?) and eventually the world! Don Matheson starred as Mark Wilson in Land of the Giants.

The ghost of Blackbeard is alive and well, and he wants the Seaview and her crew. The pirate 'drafts' Kowalski, who makes a very convincing and quite blood-thirsty buccaneer. Nelson and Crane have their hands full trying to protect the President of the United States (a guest of a Middle Eastern Shah on a nearby yacht), and regain control of their ship.

About the plot . . . Um . . . Well . . . Uh . . . Okay, here it is: You see, there are these twin leprechauns, one good, the other icky. The icky one wants all the gold that's buried beneath an underwater defense installation in the Irish Sea. The good leprechaun does his best to stop his evil brother from doing any harm . * Footage of Morton and Kowalski trapped in an underwater cave was borrowed from previous episodes. So what else is new? * Why this episode wasn't broadcast on St.

A lobster-like alien emerges from a capsule retrieved from the ocean floor. He claims that all he wants is one of Seaview's nuclear rods to power his ship for the homeward journey, but neither Captain Crane nor Admiral Nelson is convinced he can be trusted. Victor Lundin also played the neck-braced Hansjurg in Season 2's "The Menfish".

Poor Captain Crane. The things he had to go through. This time, he's in the Flying Sub, when he receives a distress call from the Seaview. He comes back to his sub, only to find it abandoned -- again. But wait, there's a force-field on the spiral stairs which knocks Crane out, and there's a stranger aboard who naturally shoots at him. Eventually Crane sees the crew, and he hears the voice of Nelson calling him a traitor. It takes about an hour, and a bullet in the shoulder (fired by guess who?), before Crane discovers aliens are testing the human race.

"But that's not the goal of a man -- of a scientist!" Admiral Nelson At an experimental station in the Antarctic, the crew discovers a 'tropical paradise' -- but most of the scientists are missing. When two unconscious survivors are brought aboard Seaview, something deadly starts to stalk the corridors. Meanwhile, the temperature outside is still rising .... * The white furry monster costume also appears in at least one Lost in Space episode.

Naval ships have been disappearing, and Seaview is on a hunt for the undersea installation responsible. They find a sea-lab that is not only well-armed but surrounded by overgrown and ferocious sea-creatures. To complicate matters, the guest expert aboard is a traitor. Various "dangerous denizens" of the deep from earlier episodes reappear here, thanks to re-used footage: there's a whale, and one of those globular-eyed bottom-dwelling monsters seen in such episodes as "Deadly Creature Below".

"You had no right -- no right to make that second dive without orders from me!" Nelson to Crane Another scientist with another artificial atmosphere (see Season 1's "The Condemned") that will revolutionize deep-sea diving. When will Admiral Nelson learn! Naturally, Captain Crane is used as a guinea pig for these dangerous experiments. And there are fatal side-effects. * A great Nelson/Crane argument takes place in the Admiral's cabin after the Captain has made his unauthorized second dive. * In this episode it is not Nelson who shoots Crane, but rather, Chip Morton. * Notice the tears of gratitude and relief in Crane's eyes after Nelson gives him the antidote at the very end of the episode. * Crane also shed a tear (from pain) in Season 3's "Day of Evil".

Alien jungle growth is spreading across Italy, and before long -- thanks to a crewman who is really an alien spy -- the vegetation invades Seaview too. The Admiral has built a device that might help, but first he and Crane have to fight their way through the overgrown corridors to prevent the missiles being used to spread the infestation even farther. * Patrick Culliton played various crewmen over Voyage's 4 seasons.

Seaview is under polar ice, trying to discover the cause of increased flooding around the world. Nelson finds out that Frost Men are in the process of melting the ice cap. The Seaview's reactor is just what they need to finish the job.

Aliens are at it again. They're planning to destroy the Earth. However, one of the aliens claims to be a good guy. Can he be believed? Will mankind survive yet another close encounter with space visitors? * Skip Homeier also appears in "The Amphibians" and "The Day the World Ended" * Kevin Hagen guest-starred in "The Shape of Doom".

"Idiots!!!" Admiral Nelson to himself. There is an imposter on Seaview. Lee Crane is the main suspect. Admiral Nelson takes Morton and Sharkey into his confidence. They must put Crane to the test to find out whether or not he's the man they know. Captain Crane is really put through the ringer in this episode! Admiral Nelson hurts his feelings on purpose, the Captain practically chokes to death from a fire in the Circuitry Room that he gets blamed for, he gets locked in a storage room, and he's driven half out of his mind by the Admiral, Morton and Sharkey. Through it all, Crane maintains his inner belief in himself.

"... but the Flying Sub's my baby!" Captain Crane to Chief Sharkey Seaview's reactor is running wild -- again. Without taking the time to don protective anti-radiation gear, Captain Crane runs into the Reactor Room to shut down the pile. An explosion renders him unconscious. Although treated in Sickbay with a special anti-radiation device, the Captain does not come out of his coma-like state. Doc can find no explanation. (Apparently, Doc hasn't read the script.) Corpsman Mallory has turned that life-saving device into a time-machine. Mallory is testing his fourth-dimension gadget on Crane before using it to enslave the entire world! A warped and insane Captain Crane from the future shoots and kills Admiral Nelson, because he believes the Admiral has held him back from achieving all he should have. Maybe he's paying Nelson back for the Krueger incident.

Seaview experiences a sudden power overload and blows up, killing all hands aboard. When Admiral Nelson (who was at the Nelson Institute at the time of the accident) hears of the destruction of the Seaview, he gets an impossible to refuse offer from Mr. Pem (who survived from A Time To Die): in exchange for the use of the sub's nuclear reactor, Pem will transport Nelson back in time to before the explosion which destroyed Seaview. Once back in time, Pem renergizes his time travel device and brings the sub back even further in time to the American Civil War. Before the crew has time to absorb this, the ship is boarded by Major General Benedict Arnold! Now Nelson has to stop Pem's far-reaching plan to take over the world and avoid the explosive disentergration of Seaview.