The best thing about the sad but generally satisfying teen drama "Death of a Superhero" is the film's wonderful scenes pairing two fine actors American audiences know very well, though not necessarily at first sight.

First, there's Andy Serkis, the superstar motion-capture performer who played Gollum in "The Lord of the Rings" trilogy; the titular "King Kong"; and Caesar, the chimpanzee leader in "Rise of the Planet of the Apes." Though Serkis often appears in his natural form in films and on television in his native England, in the U.S. we largely see his considerable skills via computer-generated characters.

Serkis' co-star in "Superhero" is former child actor Thomas Brodie-Sangster, who appeared in "Nanny McPhee," "Bright Star" and as an adolescent Paul McCartney in "Nowhere Boy." Americans probably know him best as the voice of Ferb on the Disney Channel's signature animation series "Phineas and Ferb." But in the flesh, Brodie-Sangster is an actor to watch in years ahead.

Together, Brodie-Sangster and Serkis have terrific, intuitive chemistry in "Superhero."

Serkis plays a generous, comfortably rumpled therapist and widower named Dr. King, holding an ever-present mug of tea while treating Brodie-Sangster's Donald, a kid dying of cancer but not going quietly.

Pushed by his parents — who are barely keeping themselves together emotionally — to do all the right things to combat the disease, Donald sees little point and is enraged at the likelihood of an early death.

Much of "Superhero's" story is told symbolically, through comic-booklike characters stirred to life from Donald's imagination and pen (he's a ferociously talented artist), often with a brazenly sexual element.

A nonanimated subplot concerning arrangements for a mercy tryst for Donald becomes an uncomfortable diversion late in the film. But it serves to underscore his more important relationship with a girl (haunting work by Aisling Loftus) who is clearly his soul mate.

Much of this film quickly vanishes from memory, but there's some gold here. That's pretty much the message about life itself in "Death of a Superhero."

Tom Keogh: tomwkeogh@gmail.com