A sinister, alien creature comes aboard the Lexx and possesses the ship's hapless captain, Stanley Tweedle. The ship's robot, 790, attempts to alert the crew that something is wrong with Stan, but by now they've all gotten so used to 790 abusing Stan that nobody takes 790's warnings about Stan seriously. The Web tells the story in a relatively straightforward manner, while The Net fills in the background material, explaining various plot threads and introducing others.
