Captain America #136 (1969)

"The World Below," Written by Stan Lee, pencils by Gene Colan, inks by Bill Everett. Cover pencils by John Buscema, inks by John Verpoorten.  SHIELD agents believe Captain America is dead after he and a huge gorilla (actually SHIELD biochemist Dr. Erik Gorbo) fall into a huge hole in the Earth; Their fall is slowed and halted by an anti-gravity beam wielded by the Mole-Man; Gorbo relates to the villain because they are both outcasts because of their appearance; The Mole-Man and his minions capture Cap and the gorilla; Gorbo dies, reverts to human, and confesses that he lied to start a war.

The origin of the Mole Man is retold.  Good condition.