When Olivia Villalobos finds a bloodstained love letter she endeavors to deliver it before Chief Inspector Sedeño finds it in her possession.

A city along the southern coast of Puerto Rico emerges in the aftermath of the Spanish-American War. Olivia, daughter of a drunkard police investigator who never knew the truth behind her mother's disappearance, finds a bloodstained love letter in the hidden compartment of her father's coat. Convinced it belonged to the man recently found dead she sets out to deliver it to the Labyrinth of Love Letters. A mysterious place believed to be an urban legend where the transients of forbidden love leave missives for one another. She enlists the help of Isaac Quintero to find the Labyrinth and they soon realize their quest has opened the door into Old Sienna's darkest secrets—the perils, madness and depth of tragic love.