Eloise, a grandmother portrayed by Shirley MacLaine, engages her two granddaughters in a captivating rendition of The Little Mermaid. In her version, a mermaid princess is deceived by a wizard who not only steals her soul but also forces her into a life far removed from her ocean home, enslaved to the wizard for eternity. When the girls express their disbelief in the story's authenticity, Eloise begins recounting a true tale of a girl she once knew who encountered a mermaid.
Enter Cam, a young reporter played by William Moseley, who finds himself in a challenging situation. He is responsible for taking care of his niece, Elle, portrayed by Loreto Peralta, who suffers from an undiagnosed condition without a cure. One day, as Elle plays outdoors, she starts coughing, and Cam swiftly carries her inside before heading off to work. At the office, his boss assigns him the task of investigating Locke, a man from a circus who claims to possess mermaid healing water. Driven by the hope that this water could cure his niece, Cam embarks on his investigation.
When Cam and Elle arrive at the circus in Mississippi, they are greeted by the sight of a mermaid trapped in a glass tank. Determined to uncover the truth, Cam interviews several individuals who have used Locke's mermaid water, only to find that none have experienced any healing from their ailments. After concluding that the supposed healing water is simply an elaborate scam to deceive those who wish to believe, Cam starts to suspect that the mermaid might be part of the ruse as well.
However, during a walk in the woods, the duo encounters the mermaid once again, who introduces herself as Elizabeth, played by Poppy Drayton, and explains that she can walk on land during low tide. Back at the circus, Cam discovers that Locke holds a vial containing Elizabeth's soul, which prevents her from escaping. Suddenly, Elizabeth is forced to leave them. Cam, undeterred, sneaks back into the circus and overhears a conversation between Locke and his henchman, Sid, played by Tom Nowicki. Following the entrancing sound of Elizabeth's singing, he attempts to find her, but is discovered by Locke and Sid, leading to a hasty exit.
Things take a turn for the worse when Locke kidnaps Elle, revealing his nefarious plan to use her, as she possesses the heart of a mermaid, for his scams. With impending danger looming, Cam is helped by Thora, a mystical fortune teller played by Shanna Collins, and Ulysses, a skilled fighter from the circus played by Chris Yong. Together, they set out to rescue Elle, reclaim Elizabeth's soul, and free her from her glass confines. Locke, who is revealed to possess magical abilities, pursues them relentlessly.
In a thrilling escape, Thora and Ulysses share their own tragic stories of how they were tricked by Locke into becoming part of his circus. Arriving at the ocean, they confront and defeat Locke and Sid, ultimately allowing Elizabeth to regain her soul. With her newfound freedom, Elizabeth performs a healing on Elle, revealing that all she needs to feel better is a swim, as she shares mermaid blood. In a bittersweet farewell, Cam and Elizabeth share a kiss before she dives into the sea, never to be seen again.
Feeling compelled to tell the truth, Cam submits his story claiming the mermaid's existence and exposing the wrongdoings of Locke's fraudulent schemes, though he wonders whether anyone will actually believe him. As Eloise concludes her tale, she suddenly begins to cough, and with a surprising revelation, states that it is time for a swim. The astonished granddaughters follow her outside, witnessing their grandmother transform into a mermaid, thus leaving them in awe of the wondrous truth.
