The deadly rat flu virus has changed - humans are catching it and nobody is sure why. Officer Katt is trying to blame it on the Lost World Circus and it's up to Colt to prove her wrong. But he and Birdy are trapped in the sewers, and the man who holds the key to it all is being held prisoner at DoRFE Headquarters. Is this the end of the road -not just for the circus, but for all of humankind?