After the arrival of a newly elected U.S. Senator to inspect Admiral Nelson's new weapon, strange things begin to happen, culminating with the realization that everyone outside of the Seaview appears to have disappeared from the Earth.

An old man, adrift at sea, is rescued along with a sack of toys by the Seaview. The toys take on a life of their own and begin to sabotage the ship. The toys appear to be connected to an alien space ship lying on the ocean floor.