A UFO is destroyed near the Moon by Interceptor One, but jettisons small metal canisters which Interceptors Two and Three cannot hit, even with computer-guided missiles. Moonbase warns Earth, but even Sky One cannot destroy them all. Straker decides to deal with them on the ground, so Alec Freeman and new recruit Hoyle are despatched as the nearest operatives. The canisters seem harmless but when Hoyle impulsively approaches one, he is struck down by gas. Masking his face, Freeman pulls him clear, but Hoyle then turns violent. Knocking him out, Freeman realises if any canisters landed in a town, there would be terrible riots. With no time to waste, Straker parachutes from a SHADO jet to join Freeman, and investigate another nearby landing. This is in the private grounds of the Duke of Brandon but inside, Straker and Freeman have to contend with game animals driven wild by the gas. Climbing a tree to avoid angry cattle, they are saved by a recovered Hoyle, who drives the car under the tree. The mention of shotguns by Freeman gives Straker an idea to counter other landings by canisters. Modified missiles which break up into smaller individual shells are used – just like pellets from a shotgun – and for now, SHADO has won again.