Tragedy strikes the Clarke family with the death of young Malcolm and the near-drowning of his brother Harvey. Their parents' grief splinters the family. Addison, a marine biologist, buries himself in his work, the study of the Architeuthis, a giant squid. His wife Marina, staring out at the sea, becomes more and more isolated on the icy shores of Newfoundland. Two portentous events take place on the same day: a live Architeuthis washes up on shore, and a man walks naked out of the sea and approaches Marina. The discovery of these two creatures, and the series of events that are unleashed by them, change the Clarke family irrevocably.