[3] A UFO lands in England, and takes control of the minds of two men and a woman (Linda Simmons, Daniel Clark and Clem Mason).
This is followed by Mason evading security and getting on board Skydiver 3, and destroying it by grabbing power cables as it leaves its base of operations.
Foster investigates Simmonds (following up on the strangled policeman), the last surviving 'living bomb', and takes her to SHADO headquarters unaware of what she is capable of.
[1] Calling the episode "a pretty strong addition" even if the story is "pure formula", John Kenneth Muir likens the guest characters to terrorist suicide bombers, writing that "in a post-9/11 world, this entire plot line seems even more fascinating than it may have in the early 1970s".
[5] Review website anorakzone.com ranks the episode the sixth-worst of the series, commenting that its "terrorism" theme is "rendered in pulp terms".