The Missionary and the Marine is a Christian romance between Maddie Gallagher, a missionary girl living in the Way Station with her family in downtown Naples, Italy, in 1971, and Nathan Kessler, a US Marine stationed at the Marine Barracks. The mission of the Marine Barracks is to guard the NATO base in Naples. Both Maddie and Nathan grow in love with each other, but there is a major complication that threatens their relationship. Nathan is not a Christian, and therefore he and Maddie, from her perspective, are "unequally yoked. Nathan has a dark episode from his past, something that he keeps close to his vest, that keeps him from coming to Christ. Further, his relationship with Maddie is complicated by a beautiful Roman girl named Nicoletta, who threatens to keep Nathan from his love for Maddie. Nathan met Nicoletta in a Roccaraso discotheque in an Italian ski resort during the New Years holiday. A tempestuous love affair is ignited and continues to blaze in Rome and finally in Ischia, a paradise island in the Bay of Naples. It is there where Nathan learns of something that threatens to change his life forever. Meanwhile, Maddie continues to pray day and night that God will somehow change the heart of the man she loves.