The droid crew of a galactic space freighter have turned against their master. Using the "Influence Device", beam aboard and destroy the mutinous crew.
Paradroid 90 is a top-down perspective game where you move about various decks of a spaceship encountering hostile droids. The ship decks themselves essentially consist of rooms, doors, elevators and repair stations. The repair stations repair your active droid and the elevators let you move between floors.
The overall goal of the game is to eliminate all droids on all of the levels of the ship. This is done either by shooting them up using your own droid's weaponry or taking control over them directly via a mini-game, eventually gaining control over the more powerful droids and their arsenal. After completing one ship you go on to a new one with a different deck layout.
The various droids have different speed, resilience and weapon strength, but the stronger droids also typically have higher circuit integrity making it more difficult to control them for long, thus balancing the use for high lever droids on low level decks.