These days, "Heatwave" is a pretty much totally forgotten film, but it's hard to see exactly why that is. Regardless of how the storyline might personally appeal to you, it's an exceedingly well-made and acted film. Judy Davis (in one of her very first roles) creates a very compelling character, a lonely and driven personality that begs you to follow along in her obsession. The setting - a heatwave over the Christmas/New Year season - helps the dramatic sense immensely, though it may be a bit disconcerting to the snowbound North American viewer. Richard Moir is also very good here, an actor who spent most of his career playing invisible roles in invisible movies.
Phillip Noyce went on to do a lot more well-known films, and he's a huge part of what brings it all together. In spite of that, he's goes too far on certain visual manipulation in a film that never really invites it. There's a political edge to the screenplay, which tends to push the viewer away, but a personal side that draws you in. For someone personally engaged in the subject matter, this would be a perfect film. And I liked it a lot.