The three Interceptors are ordered to return to base without firing upon an approaching UFO but, as they are shown turning, it's obvious that a standard stock shot showing that all three have fired their nose-cone missiles is used.
It is established early in the series that the aliens breathe fluid. If they are exposed to Earth's atmosphere, they age rapidly and die. However, the one in this episode is exposed for several hours but doesn't seem affected..
The alien's face is green, but his hands are flesh-colored. This is because the aliens' helmets are filled with a green liquid which they "breath" while in space.
Philip Madoc's (Steve Rutland) name is misspelled in the ending credits.
Mrs O'Connor, the old lady is blind, yet sitting in her rocking chair all alone, she has the lights switched on in her cottage.
Straker's ex-wife furiously blames Straker for the injury and then death of their son. However, Straker's actions have no influence whatsoever on his son's death, which is wholly due to Straker's ex-wife's cruelty towards their son. He should be outraged by her behaviour, not she by his.