Greg never wanted to be a father. The arrival of his son Mark threatened to put a dent in his hobbies, (glass-blowing) stall his career (dealing weed), and strip him of his youth. He shouldn't have worried though. 25 years on and Greg's life is unchanged; he still blows glass, he still grows grass, and in Greg's mind he never even had a son.
In Mark's mind he never had a father. Now a young lawyer with a promising future and a beautiful soon-to-be fiance, Mark is everything Greg is not. Driven, ambitious, and self-sufficient, when asked about his absentee dad Mark simply replies "He died in a river."
When Greg's own degenerate father calls him to his deathbed for some final words, he reveals a secret kept silent for 25 years: Mark is actually Greg's half-brother.
At first he is enraged at the revelation, but soon comes around to the idea. He never wanted to be a dad, but he has always wanted a brother, someone to share his hopes, dreams, and clay vase collection with. So Greg devises a plan to bond with his new-found sibling, make some new weed contacts, and attend a Dave Dobbyn concert in the Coromandel all in one fell swoop.
Gassing up his '98 Honda Civic, Greg kidnaps Mark from work and drags him off on the road-trip of a lifetime.