When Dr. Savant--mad leader of a magic-hating 30th century suicide cult on the planet Fawcettworld--blows up the Rock of Eternity, the heroine from a future even more distant than the Legion's is stranded in the 30th century!
Hurled through time thanks to an explosion of the Rock of Eternity, the super-heroine Thunder emerges in the 30th century with the debris of the Rock. Learning she has journeyed from the 20th century she was visiting back into the future by several Legionnaires, Thunder incorrectly assumes she's near her home time of the 85th century. She flies to her homeworld of Binderaan only to find it hasn't even been colonized yet, finally accepting her situation. When Fawcett World, also tied like Thunder to the Shazam mythos, is under attack, Thunder assists the Legionnaires in defending the planet. At the end of the adventure, she is invited to stay with the Legion and accepts membership into the team assigned to the Legion Outpost.