This sci-fi family film tells the story of a couple of kids who discover a mysterious box that contains some strange devices they think are toys, but as the kids play with these so-called toys they develop higher intelligence levels.
It all begins with average 10-year-old Noah Wilder (Chris O'Neil), who enjoys video games and is a little bored with his humdrum life, and his sister Emma (Rhianon Leigh Wryn), who is quite smart for a 5-year-old. Their parents Jo and David (Joely Richardson and Timothy Hutton), who make life comfortable for the family, decide to take a vacation. Jo is a stay-at-home mom and David is a dad who works long hours, so a break away from everything is a blessing. While relaxing at their beach house, the kids find a strange box washed up on the sand. Inside the box Noah and Emma find several interesting things: a crystal shaped like a card, a meteor-type rock, a sea shell, and a stuffed rabbit doll. This rabbit doll whispers to Emma that its name is Mimzy.
The mysterious rabbit Mimzy telepathically communicates with Emma, allowing her to develop special skills. Noah takes to listening to the sea shell and he develops science skills, which catches the interest of his science teacher Larry White (Rainn Wilson) and his mystic girlfriend Naomi Swartz (Kathryn Hahn). When Emma says that Mimzy contains a most serious message from the future, a scientific scan imposed by Homeland Security and the FBI shows Mimzy is part high-level electronics and part organic. It seems that Mimzy is from the future and is trying to save mankind. The film develops into a cloak and dagger caper with a dash of action. The plot is quite involved and intricate, but simple enough for the young audience to enjoy given the moral aspect of doing the right things in life and tackling challenges.