Mera is the new girl at Super Hero High, and when Wonder Woman takes Mera under her wing, Wonder Woman's best friend Bumblebee is overcome with jealousy. Despite her feelings, Bumblebee accompanies Mera and the Super Hero Girls on a field trip to Atlantis. But when they arrive, Atlantis is missing! Mera is horrified when they discover that Brainiac has shrunken and stolen Atlantis with the Atlanteans trapped inside! The Super Hero Girls must work together to defeat Brainaic and, along the way, Bumblebee must learn the true meaning of friendship.