A strange UFO was spotted crashing into the ocean not far from the coast of California. With Admiral Walter Tobin on board, the Seaview is sent to investigate. The submarine is sucked into a vortex caused from the alien ship and is severely damaged. The UFO sends out a small mini saucer and it attaches itself to the Seaview access hatch. Viewing this as an invitation, Admiral Nelson boards the mini saucer and he is taken into the UFO. Inside, Admiral Nelson discovers an alien that looks exactly like himself. The alien threatens that unless he can leave Earth the planet will be destroyed. Admiral Nelson returns to the Seaview and obtains fuel for the alien, and the visitor leaves.