Horatio Caine and Marisol Delko are one of the main couples of "CSI: Miami". Horatio is the Head of the Miami Crime Lab and Marisol is Eric Delko’s older sister. They first met shortly into the beginning of the season, when everyone on the CSI team noticed that Eric had somewhat began to neglect his responsibilities and later got into trouble when he was accused of taking drugs.

When Marisol learned of this, she came and explained to Horatio that Eric has been taking care of her, revealing she is currently sick with breast cancer and marijuana helps with her treatments. Marisol is willing to come forward to help Eric, but Horatio is able to prevent this, saving Eric’s job and proving his innocence and preventing their personal and private lives to become caught up in an internal investigation. Horatio and Marisol would later meet again when Marisol got arrested on a serious drug charge when she was caught buying marijuana in the park for her cancer support group. Horatio investigated the matter, intending to do everything he can to help Marisol and was able to dismiss her charges.

During this time, an attraction quickly develops between Horatio and Marisol and following the investigation, Marisol wishes to thank Horatio for his help by making him dinner. Horatio happily accepts and they begin a romantic relationship. Although briefly concerned about Eric and how he’ll feel about their relationship and how it’ll affect his friendship with Horatio, Eric assures he happily approves of their romance. However, Eric warns Horatio that Marisol is more sick than she appears and may only have months left to live. Horatio assures Eric he can live with that and intends to make the most of whatever time he has with Marisol.

Since then, Horatio and Marisol form a strong and loving relationship throughout the season. Horatio supports Marisol throughout her cancer treatments and encourages her to live her life and Marisol brings joy, love and hope into Horatio’s life. Horatio becomes very protective of Marisol when she is caught in another investigation, this time as a witness when she and several women were held at gun point and robbed. When one of the robbers breaks into Marisol’s home, Horatio tells Marisol to stay with him until the threat is over. Towards the end of the season, Horatio and Marisol’s love for each other has grown so strong to the point they both decide to get married.

Everyone is happy to learn of Horatio and Marisol’s upcoming nuptials, but Eric is unsure and apprehensive as he wants to focus on Marisol’s recovery, but later accepts Horatio and Marisol’s marriage and attends their wedding at city hall. However, Horatio and Marisol’s life together ends before it starts as Marisol is murdered by the Mala Noche gang, leaving both Horatio and Eric devastated and heartbroken and set out to avenge her. Following Marisol's death, Horatio is left a widower and continues to miss, love and remember her throughout the series as he treasures they time they had together.