Tom (Michael Fassbender) is a veteran who has worked on the front lines. Now, he takes his wife Isabel (Alicia Vikander) to a small island in Western Australia and becomes the keeper of the lighthouse there. The solitary life on the island makes the relationship between Tom and Isabel better. The two wait for the child in Isabel's belly to grow up slowly in joy. What the couple did not expect was that an accident caused Isabel to miscarry, and the death of the child made Isabel fall into despair. One day, a boat was washed ashore by the waves. In addition to the body of a man on the boat, there was a baby. The ecstatic Isabel begged Tom to agree to let her take in and raise the child. Although this practice violated Tom's principles, he still agreed.