Crewman Number 2 betrays Captain Nill and confines him to quarters. Number 2 takes control of Dave and wreaks havoc on New York City so that he can make his way to the Hudson River in order to suck it dry to return the salt to their home planet.
In the middle of it all, Crewman Number 3 frees the captain, who overrides Dave's controls. He stops the River from being sapped before being approached by the police, and later the FBI.
The crew makes their way to an escape pod in Dave's shoe, and leave Earth.