Fantastic Four #159
Continued from last issue... The Fantastic Four travel with Quicksilver to the Hidden Land, which has been taken over by Xemu of the 5th Dimension. When the FF lands in the area, they are easily taken prisoner by Xemu's forces, and Xemu warns them that if they continue to take aggression towards him they will use the Thunder Horn on the world.
Breaking free, the FF fight off more of Xemu's men and when Xemu threatens to use the Thunder Horn once more, it appears as though the Fantastic Four retreat so as not to trigger an attack. However, the Invisible Girl has been their ace in the hole the whole time. Having secreted aboard the FF's pogo plane, she would use her invisibility powers to help free the Inhuman royal family including Black Bolt (The "ammunition" to the Thunder Horn.) The FF reappear and with the help of the Inhumans crush Xemu's invasion of Earth's dimension and smash his Thunder Horn.
Afterwords, Xemu and his men are returned to the 5th Dimension and taken into custody by the authorities there. With Sue back in action, the group contemplates changing their name to the Fantastic Five, until Medusa explains that she can no longer be away from the Great Refuge any longer and decides to stay with Black Bolt. To celebrate Sue's return to the Fantastic Four, Johnny decides to discard his orange and yellow costume in favor of the more traditional blue FF uniform, as a symbol of the teams reunification.