The game is generally played as a simulation that allow the player to strategically send emergency forces (rat exterminators, police men, fire men and eventually army troops) to areas where the rat threat has spread and provide them with available equipment. Also the player can get ten available researchers to develop addition weapons, defenses and super weapons to keep the rats at bay and to provide useful information to progress in the game. Should the rat threat reach beyond the London limits, the Research center, the Government center or Harris' apartment or if all emergency forces are lost, the game is over.

In between the simulation game play, the game will suddenly switch to the role of a playable character in a randomly chosen text adventure scenario. The player has to select one or more verbal options to perform actions to allow the character to survive against the rat threat and avoid getting killed. While it is not crucial to keep the characters alive, saving them grants the player additional rein