Kill Straker!

[3] Col. Paul Foster and Captain Frank Craig are piloting a lunar module when it is approached by a UFO.

Foster pulls a gun, a bullet punctures Moonbase's sphere and the two pass out from lack of oxygen.

Now back on Earth, Foster is placed under hypnosis by Dr.Jackson which reveals that the aliens mentally implanted the impulse to kill Straker.

to be one of UFO's poorer episodes, John Kenneth Muir criticises the characterisation, arguing that despite Foster's highly unusual behaviour his colleagues are very slow to realise what has happened to him.

Muir also finds the premise unoriginal, noting that the idea of "sleeper agents" had been explored in earlier episodes.