When a new alloy is stolen, Oscar sends Steve to investigate. He eventually learns that the ones who stole the alloy have used it to recreate the Russian space probe, he encountered before. Now they have to find a way to stop it.

Season 5 episode 16 The Lost Island is actually two episodes, part 1 and part 2. In part 1: the OSI agency loses one of its satellites, which crashes on a remote ocean island, and is now cracked and leaking neutron radiation which is negatively affecting the other-worldly humanoids that inhabit the island and electromagnetically cloak it in invisibility. A decision is made by the aliens to send Da Nay, a young alien woman, to the U.S. to find and bring back a serum that will boost the aliens' immunity and thus allow all the aliens to leave the island and survive with the human population. In part 2: Da Nay (Robin Mattson, who plays Heather Webber from the "General Hospital" soap opera) obtains the serum and returns to the island, where Steve Austin has found a way in past the protective barriers. Spoiler: Torg (Jared Martin, who plays Dusty Farlow on "Dallas:), one of the radiation-influenced young male aliens who feels a somewhat barbaric attraction to Da Nay, turns monstrously evil from the radiation, as do other exposed aliens. Steve Austin learns how to use the same radiation to reverse the process and restore the unity of the aliens. Steve and the satellite are recovered, and the alien race are once again kept secret and cloaked in invisibility.