Sunderland, who starred in The Luminaries, says The Stranger is based on a true-life sting operation. It marks the second feature of Australian actor, writer and director Thomas M Wright.
He auditioned for two parts - The Controller, a senior detective in charge of the logistics of the undercover operation, and The Cleaner, an underworld figure whose job it is to clean up any "mess".
"In the end, I was offered both roles, after Thomas decided to make them the same person," he says.
"Most of my scenes were with either Joel or Sean or both. So, no pressure. We filmed all around the hills on the outskirts of Adelaide.
"To say I learned a lot from them is an understatement. They both have very different processes yet were both generous and collaborative."
Sunderland is on a movie roll with more than 20 features to his credit. He has two new films to follow The Stranger, including a prequel to Martin Henderson's horror movie X, called Pearl.
Both American movies were shot back-to-back in New Zealand, in secret, by writer/director Ti West early last year.
Earlier this year, Sunderland wrapped shooting Aussie movie Super Rosa, directed by Sauro Morganti. It is described as an unconventional love story examining the unhealthy role that dependency can play in our personal relationships.
Another Kiwi in Cannes is Fergus Grady, festival director of the French Film Festival Aotearoa, which launches on June 1. He's on the lookout for the best of the fest for next year's line-up.