A reluctant Solomon (Colin Baker), along with his former associates Egan (David Troughton) and Saul (John Wadmore), have (they think!) escaped Earth and returned to their own dimension. But a mysterious force returns them to Earth and drops them right into the middle of a top-secret experiment involving a young girl's mind powers. They soon find that the experiment has gone wrong and unleashed something deadly...and unless they can find a way to stop it, they and the experiment's team members will all soon be dead!

The Airzone Solution takes place in a future Britain where pollution has reached a point where the populace must often wear filtration masks when they venture outside. AirZone, a powerful corporation, signs a lucrative deal with the government to deal with the problem. The public is told that AirZone plans to build giant filtration plants to clean the atmosphere, but environmentalists are skeptical, especially when people begin dying and disappearing around AirZone facilities.