Ondine starts out with a fisherman (with the oddly un-Irish name of Syracuse) who plies his trade with a small boat off the coast of Ireland. Him and his fishing boat are necessary elements to the story, because the tale starts when he pulls up a beautiful young woman wearing a bedraggled gray dress in his net. Initially thinking that she’s dead, he at first thinks of reporting his unusual catch to the authorities, but she turns out to be alive but unconscious, and she quickly revives after he gives her CPR. She makes it clear that she doesn’t want contact with anyone else, and being a fisherman in a remote area, who is lucky enough to have inherited a house from his mother near his fishing grounds, he is initially able to accommodate her wish to hide from the world.

He tells only one person about this unusual occurrence: his young daughter, who suffers from kidney failure and uses a wheelchair, had no book to pass the time during a dialysis appointment; to entertain her he tells her about the strange woman he fished from the sea, claiming that this story is a self-created fairy tale. Having just learned about the Scottish folkloric creature, the Selkie, she comes to the conclusion that this woman has to be a Selkie.

When she meets the woman and finds out that she is more than a fairytale, she starts reading up on Selkies and asking the woman questions. The woman gives her name as “Ondine” (implying that she is indeed a water spirit of some sort), and eventually acknowledges some Selkie characteristics and behavior as the movie goes on. Though the woman initially denies it, the girl and later others in the small town start seeing evidence to support the theory that she is a Selkie.

Most convincingly, when Ondine goes out on the fishing boat with Syracuse and sings, his lobster pots and trawling nets become strangely full. Her attempt to conceal something is taken to be an attempt at “burying her seal coat”, and the appearance of a strange and hostile man who wants to force her to go away with him though she wants to stay with Syracuse and is fast establishing a relationship with him is credited to the folklore concerning “the Selkie husband”. The viewer is left to wonder if she is indeed a Selkie or something similar.

While this movie does use the traditional imagery of the cute little disabled kid in the cute little wheelchair heroically enduring repeated dialysis treatments and patiently waiting for a donor kidney, and indulges in the further unreality of making the girl able to walk for some distance when her new motorized wheelchair becomes temporarily disabled after some able-bodied kids ride it into a big puddle, it is more realistic about physical disabilities and the lives of kids who have them than most other pictures involving a disabled juvenile character. This is perhaps because it is not, strictly speaking, a film about a disabled kid, but rather, a film containing a kid who happens to have some unnamed condition that involves kidney failure and the use of a wheelchair in wheelchair-unfriendly small-town Ireland. The first scene depicting the girl in a manual wheelchair shows us that her father routinely rides her straight over high curbs and cobblestones, and carries her into the car, up stairs, etc. Neither wheelchair ramps nor elevators are anywhere in evidence, those in the know are well aware that she can’t be carried like that forever. The girl somehow goes to school and to the local library, apparently others (her mother and stepfather) carry and chauffeur her as well. Nobody seems to have a van with a wheelchair lift; when Anna gets her power chair, she has to drive herself alongside her father’s car to get home. Though she has a normal pre-teen’s preoccupations, such as watching rock groups on TV and curiosity about the budding relationship between Ondine and her father, her life comes with some unusual risks built in: her stepfather looms as a menacing presence whose conduct and contact with her looks suspiciously on the verge of improper and abusive; her biological father got sober only because he realized someone had to be in order to properly fulfill parental responsibilities to her; his fall off the wagon threatens Anna as well as himself.

Ironically, it was an evening at the pub for her mother and stepfather in which both get inebriated and her mother rode in Anna’s power wheelchair which leads to the death of Anna’s stepfather in an unexpected car crash. He turns out to have a donor card and to be a perfect match for a kidney for the girl. This good luck-bad luck situation is attributed to the wish-granting power of the Selkie after the girl had asked the woman to make her better. Unlike in a lot of movies with a disabled character, the wish articulated by the little disabled girl, “make me better”, did not mean “remove the need for a wheelchair” but rather the life-threatening crisis of the kidney failure.

The true identity of “Ondine” remains a mystery until near the end of the movie when a less supernatural theory of how she came to be where and what she is comes to be revealed. We come to realize that Anna has created a bit of a fantasy for herself in order to cope with the tremendous stresses of her illness instead.