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A condition-critical red alert comes in from Oceanographic Research and 7-Zark-7 identifies a murky brown cloud of pollution spreading through the oceans, which instantly kills the fish it touches. Not only are all the fish dying, but so are the birds feeding on them. Suspecting Zoltar is behind this environmental hazard, 7-Zark-7 dispatches G-Force to collect a sample of the pollutant.

When Chief Anderson analyzes the sample he finds it is made up of an alien chemical. Nothing like it has ever been found before and the Chief believes it has to be from Spectra. Unless the source of the pollution can be found, the Earth is doomed. On their mission to discover the source of the pollution, G-Force makes nothing of three oil tankers while on underwater patrol. 7-Zark-7 suddenly alerts G-Force to an object that looks like a mechanical shark cruising near the Phoenix. He determines it is a massive weapon and orders the team to prepare their torpedoes. They fire on the craft and destroy it, but it turns out to be a Spectra carrier that releases more of the deadly pollution into the sea. The team heads for the air again when they notice the seas are filled with the murky pollution. But Tiny has a question about the three tankers which are still in the area: They're not flying any flags and they're not traveling in normal shipping lanes. Mark decides to take his rocket sub from the Phoenix and go back underwater for closer look at the tankers.

Mark notices additional Spectra carriers under the surface that are entering hatches on the bottom hull of one of the tankers. A problem with his own sub forces Mark to take emergency refuge in the tanker with the Spectra carriers.

Zoltar is on board the main tanker and he notices the Phoenix on one of his monitors. He orders the three tankers to transform and to activate their Gravity Ray gun. The tankers join together into a larger ship and fire on the Phoenix with the weapon. When they hit the Phoenix, it is completely trapped and cannot escape. No matter what Tiny attempts, he can't pilot free and the Phoenix's hull begins to crack.

But on the tanker, Mark surprises Zoltar by showing up behind him on the bridge. He tells the Spectran leader he's reprogrammed the Gravity Ray to self-destruct. Mark then orders Zoltar to surrender. The Gravity Ray suddenly stops working and the Phoenix is able to fly to freedom. Zoltar takes advantage of the momentary distraction to open an escape hatch and drop through. Mark follows him just as the sabotaged Gravity Ray swings over and begins firing on the tanker itself.

Zoltar makes his escape in a small ship as the tanker is ripped apart by the Gravity Ray. Mark escapes the ship and signals the Phoenix from the ocean where G-Force is able to pick him up. Fortunately for G-Force and Earth, the tankers were carrying cylinders of liquid to deactivate the terrible pollutant. With the tanker destroyed, the cylinders break open and release the antitoxin, making the seas safe for life again.

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Susan appears for the first time

1-Rover-1 appears for the first time

Tiny keeps rare goldfish

The Phoenix carries a rocket sub

Princess is in charge of communications and the sonar station on the Phoenix

7-Zark-7 says he still has not met any of G-Force in person

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