"God Only Knows" is the fifteenth episode of the series.
Just as “Army of Two”, Carole & Tuesday’s debut song, is spreading around Mars, the girls receive an invitation from Desmond, a solitary artist who’s known as a living legend. Carole & Tuesday discuss their dreams while listening to a Desmond song selected by Roddy, then visit Desmond’s mansion to find out why they’ve been invited. Meanwhile, Tuesday’s mother Valerie, who’s running for president of Mars, participates in a debate with the current president.
The debut song of Carol and Tuesday "Army Of Two" is spreading around Mars. Carole and Tuesday started to do exercise since they believe stamina take a huge part in being professional artists. While jogging, they met Gus and Roddy and told them that they were invited by Desmond.
That night, Carole and Tuesday were outside of their apartment listening to Desmond songs that Roddy send to them while staring at Earth. While staring at Earth, they said their wishes.
Carole and Tuesday, together with Gus and Roddy went to Desmond's place. Upon arriving at Desmond's place, they were welcomed by an A.I. and was led to Desmond.
They saw Desmond sitting in a wheelchair singing "Miserere mei, Deus". Desmond stated the reason he invited Carole and Tuesday is that they were frank, honest and sincere. Desmond revealed that he/she is an androgyne. Desmond told them that all of his/her songs were written for the man he loved.
Refusing to take medication, Desmond said his last message to the world and sung "All I See".