Paula Beer is a young German actress who has been generating a lot of excitement over the past five years. Virtually every time she makes a movie, she gets nominated for major awards. She won best young actress at the Venice Film Festival in 2016 for “Frantz,” and recently won best actress at the Berlin Film Festival for “Undine,” which opens Friday, June 4,in theaters and video on demand.

What makes her so good? Well, there’s really no answer to that, but here is one, anyway, by way of an example: In one of the first shots of the film, she is sitting at a cafe with a man. She is doing nothing obvious. She isn’t crying. She’s just looking at him. Yet within three seconds, maybe two, the thought is communicated. She is in a relationship, and the man is breaking up with her.

If you stream this movie, you can rewatch these early moments and try to figure out how she does this. But a good guess is that she is not actuallydoinganything. She’s putting herself into the imaginary circumstances of the scene andfeelingsomething. And we’re just reading her face, as we might if we were inches away from her.

现场变得有趣。水女神(er) informs the man that he can’t break up with her, because if he does, she will have to kill him. She doesn’t say this as if she’s jealous. She says it as though she has an obligation to kill him under the circumstances, and it turns out that, in the weird world of this movie, she really does.

“水女神”是基于一个我h, perhaps more popular in Europe than in the United States. (Ravel’s piano piece, “Ondine,” is based on the same myth.) According to legend, Undine is a water nymphwho becomes human if a man falls in love with her. But if the man falls out of love and chooses another woman, she has to kill him. In some versions of the myth, she dies, too. In the more common version, she must return to the water.

The obvious thing to expect here is that writer-directorChristian Petzoldis using the “Undine” myth as a metaphor. But no, he’s doing the actual myth. Thus, Undine, who works as a historian and tour guide, is one argument away from committing homicide and escaping into the sea.

That’s a strange idea for a love story, but maybe not so strange, once one considers that being abandoned by love iskind oflike getting thrown back into the sea from which we came. Perhaps that’s a stretch, but in any case, Undine’s water origins are no impediment to an audience’s investmentin her romantic life. The fact that she might die, or have to kill somebody, or take up residence in the ocean are just literalized versions of the emotional stakes people face in any intense romance.

Most of the movie details a sweet relationship she has with an undersea diver (Franz Rogowski), who is as crazy about her as the first boyfriend was indifferent. The purity of their connection is compelling in itself. As for the myth, hey, we all have our baggage. The fact that she’s a potentially lethal sea creature — that’s just hers.

We still want her to meet a nice guy and — for both their sakes — to keep him.

M“Undine”:Romantic fantasy. Starring Paula Beer and Franz Rogowski. Directed by Christian Petzold. In German with English subtitles. (R. 91 minutes.) In theaters and video on demand starting Friday, June 4.