Mia and William venture into the Glades on a dangerous mission. There they run into Dinah, Roy and Zoe who deliver some devastating news. The flash forwards share highlights from Mia's childhood with Felicity.
Tony Stark tries to revive a dormant peacekeeping program -- a self-aware, self-teaching artificial intelligence known as Ultron. The plan backfires when Ultron decides that humans are the enemy, and Earth's Mightiest Heroes must stop his fatal plans.
While doing research on a space station, Reed Richards, his girlfriend Sue Storm, his partner Ben Grimm and Sue's brother Johnny are changed by cosmic rays. They decide to use their new powers to put a stop to the plans of the evil Doctor Doom.