Noah Wilder (CHRIS O'NEIL) is an average 10-year-old boy with average grades at his Seattle school. With his father, David (TIMOTHY HUTTON), always busy working, Noah spends most of his time with his younger sister Emma (RHIANNON LEIGH WRYN) and their mother Jo (JOELY RICHARDSON). When the three head off to their lake vacation home, the siblings discover a strange box in the surf.
Inside are various mysterious objects, as well as a stuffed bunny toy that "talks" in a somewhat gurgled fashion. Emma quickly adopts "Mimzy" as her own, but little do the kids know that those items have been sent from the future -- via a desperate scientist -- in a last ditch effort to save the future of humankind from their polluted world.
For the kids, they're just fun, if unusual things that soon give them unique supernatural powers, a development that doesn't escape the notice of Jo or Noah's science teacher Larry White (RAINN WILSON) and his new-age fiancée, Naomi Schwartz (KATHRYN HAHN). Things get even more complicated when one of the items causes a massive blackout across half the state.
That draws the attention of Homeland Security regional director Nathanial Broadman (MICHAEL CLARKE DUNCAN) who assigns his team to find the source of the outage, believing it could be terrorism based. Realizing they're in trouble but not understanding the ramifications of their actions, Noah and Emma try to figure out what to do with their magical find.