Action Comics #402

Synopsis

THIS HOSTAGE MUST DIE! / FEUD OF THE TITANS! Superman discovers that the red jewel is drawing energy from a red sun, and frees himself by blocking out its light; Then he discovers that Frank Haldane has found the treasure of Montezuma, and is attempting to steal it with a mechanical mole of his own design.  Superman and Supergirl are made hostile to each other and goaded into a super-feud when fumes from a brainwash bomb they are disposing of in the Fortress of Solitude's disintegration pit combine with Kryptonian elements there and make them hate each other.