The series takes place in the fictitious city of Mariner Bay, California, which was built on an ancient demon burial ground.

The Rangers were aided by a team of scientists and engineers led by Miss Angela Fairweather, and operated out of the Lightspeed Aquabase, an underwater military compound that also deters the hydrophobic demons from directly attacking the base.

Trakeena, the enemy of the Galaxy Rangers, returns to destroy Earth as vengeance for her defeat, but first, she must absorb enough human life force for power.

Olympius and his demons enter the fray, sabotaging Trakeena's power drain and mutating her into a giant, maddened creature.

While the rangers try to free Trakeena's hostages, Carter and Leo defeat Triskull and are aided by Damon and Kendrix, but they are soon blasted out the window.