Frank Adler is a single man raising a child prodigy, his spirited young niece Mary, in a coastal town in Florida. Frank's plans for a normal school life for Mary are foiled when the seven-year-old's mathematical abilities come to the attention of Frank's formidable mother Evelyn, whose plans for her granddaughter threaten to separate Frank and Mary.

When mysterious spacecraft touch down around the world, a team, including linguist Louise Banks, is brought together to investigate. As mankind teeters on the verge of global war, Banks and the team race against time for answers, and to find them, she will take a chance that could threaten her life, and quite possibly humanity.