My interpretation of this song is based on the fact that this song was usually recorded and played live as a medley with "Teenagers from Mars".
As "Teenagers" is about aliens impregnating adolescent girls, I believe this song is about the aftermath of the latter incident, with the mating partners of the martians reacting strangely. The line, "With your heart in your throat/And the other alive", could be referring to the children giving birth to the inhuman offspring orally, and possibly dying.
My interpretation of this song is based on the fact that this song was usually recorded and played live as a medley with "Teenagers from Mars". As "Teenagers" is about aliens impregnating adolescent girls, I believe this song is about the aftermath of the latter incident, with the mating partners of the martians reacting strangely. The line, "With your heart in your throat/And the other alive", could be referring to the children giving birth to the inhuman offspring orally, and possibly dying.