I think anyone can be forgiven for thinking that Willem Dafoe is absolutely, psychotically nuts. Sure, he can play sympathetic characters, like in “Platoon,” but he just seems so much more authentic playing weird guys in, ideally, weird movies.

In “The Hunter,” out Friday, he plays a weird guy in a not-very-weird movie: Martin David is a mercenary commissioned by a mysterious corporation to track down and kill a Tasmanian tiger, an animal that may or may not be extinct.

The film is pretty good, but the most enjoyable moments come when Dafoe shares the screen with the two children in the film. His scenes with them (there are only a couple) are hilarious — and quite a jolt in what is fundamentally a pretty dark story.

Peppy, blond Morgana Davies, in particular, contrasts with Dafoe’s innate weirdness in such a wonderful way. Her openness slams up against his reticence (and his reactions, particularly when she and her brother hop into the tub while Dafoe is soaking) so interestingly that the two sum up Martin’s basic struggle: civilization versus nature, family versus solitude. It’s clear Davies is filling a stereotypical role — a bright spot in a dark life showing a lonely man what love is — but she does it with such unselfconscious joy that her performance transcends cliché and becomes something truly special.