Following a bomb scare in the 1960s that locked the Webers into their bomb shelter for 35 years, Adam now ventures forth into Los Angeles to obtain food and supplies for his family, and a non-mutant wife for himself.

At the University of Chicago, a research team that includes brilliant student machinist Eddie Kasalivich experiences a breakthrough: a stable form of fusion that may lead to a waste-free energy source. However, a private company wants to exploit the technology, so Kasalivich and physicist Dr. Lily Sinclair are framed for murder, and the fusion device is stolen. On the run from the FBI, they must recover the technology and exonerate themselves.

When a cryptic note is passed to young Bert Hale by a stranger, he and his three friends inadvertently hold the key to unravelling the sinister plot to assassinate a Russian premier visiting Los Angeles.