Chicago, 2055. Charles Hatton has made a fortune by founding 'Time safari', which offers rich 'big game hunters' short time travels to kill off dinosaurs just before their natural death. When scientist Travis Ryer notices the weather and wildlife are not behaving as usual, he consults Dr. Sonia Rand, the contractually invisible inventor of the supercomputer which controls time. They soon face 'time waves', each worsening the effects in 2055 of evolutionary distortions, lower lifeforms first. They attempt to identify and rectify the past alteration, but each attempt gets harder in their distorted present.