Story told to the public before they experience the ride-installation:
The biologist Dr. Fraser used to make genetic experiments in an old laboratory on large mammals. This was until, however, a very serious incident. Special strains of genetically manipulated creatures broke out of their cages. Since then they have been hiding in the network of ventilation shafts which supplies the laboratoires and cage rooms with fresh air.
Dr. Fraser and his assistants have been missing ever since...