Piper Hathaway discovers that her husband Joel is thinking about leaving her and their two children. She loves her husband and doesn't want to lose him. What to do? Desperate to reconnect with her husband, Piper arranges a Christmas vacation at the Last Chance Motel in Key Largo, where it's been said miracles happen. Piper prays for one, but everything seems to be turning out wrong.

The children get into trouble with the law, and Joel is rude and distant. Piper is ready to throw in the towel and ask Joel for a divorce.

But something holds her back. Perhaps it is the ethereal singing Piper hears in the lagoon each day at dawn. Eva Hanover, the motel's owner, says the magical singing comes from a siren of the sea. Legend has it whoever catches a mermaid singing will have something wonderful happen in her life. Piper doesn't believe mermaids exist, but she is still drawn to the water's edge each morning in hopes the old sea tales about mermaids are true, because she does need a miracle. And Piper needs one in a hurry!