The Last Love Letter shows how three separate women can find love even when they're not looking for it. However, their object of affection, Juan Dominguez, doesn't have pure intent. After deciding prison life is not for him, he is set on finding his way out, no matter what it takes.

The one thing Juan does have going for him is the ladies find him irresistible. Two of the three women simply love the idea of falling in love with the same man, and neither of them is aware of this since he is their best-kept secret.