Lieutenant Kate De Marco, an army nurse, and Captain Robert Coleman, an infantry officer, met in the Philippines in 1940. Finding themselves in one of the most romantic locations in the world, their love grew even as the winds of war threatened to drive them apart. After the bombing of Pearl Harbor, their lives changed completely, as American and Filipino soldiers surrendered to the Japanese in Bataan. Kate and Robert were separated in the melee.

Evacuated to the relative safety of nearby Corregidor Island, Kate kept a diary, where she recorded her longing for Robert's safe return. Meanwhile, Robert opted not to surrender and instead swam the precarious two miles from Bataan to Corregidor in search of his love. As the Japanese threatened to take Corregidor, Kate hid her diary in the walls of an underground tunnel, where it stayed for seventy years.

In 2012, Lisa Newhouse and Brandon Wales, two graduate students from the University of Tennessee, travel to Corregidor with a study group and discover Kate's lost diary. Inspired by her words and her love for Robert, they too admit their shared feelings. Although the intersection of their lives with that of Kate and Robert is coincidence, the diary leads them on a journey, which will change their lives forever.