In the concluding episode of the first series, the crew head for Mars after tracking the alien mother ship, however there's a saboteur on board who threatens to destroy the Nemesis crew. Believing that the ship's computer has turned against them, Sally has to shut down the system before it's able to destroy the ship. Eventually, with the help of Ox and Wu Oof, she manages to pull the plug on Daphne, but before she can escape the core closes and the automatic destruct system is activated.
With only moments remaining, the crew leave the ship and molyport to Earth. They look to the skies waiting expectantly for the ship to explode beyond Earths atmosphere leaving them stranded in the 21st Century. When nothing happens the real saboteur reveals himself just before the crew realize that one of them has been left on board and that person must save the day. That individual is no other than the less then brilliant Reginald Montague Duck, janitor of the stars.