Green Arrow is the first hero to be added to the membership of the JLA as Gardner Fox crafts a story suited to the Emerald Archer. When a mystical arrow appears before the assembled Justice Leaguers, it declares itself to be from the villainous Carthan who has captured Green Arrow and who is now challenging the JLA to overcome the three engines of doom he has placed strategically around the earth.

Splitting into three teams, the League manage to disarm the engines of doom, but then find themselves trapped inside a huge diamond from which there is no escape - from the inside. The only way out is if Green Arrow can hit the weak spot in the diamond with pinpoint accuracy. Can the Emerald Archer rescue his new team mates?