Matthew Mcconaughey hasn't even told his wife the 'Interstellar' plot.

The actor has signed on for a mystery role in Christopher Nolan's new movie, and the sci-fi project is so shrouded in secrecy that McConaughey hasn't even been allowed to disclose any details to his wife, Brazilian model Camila Alves.

Quizzed by MTV about the futuristic film, which follows a team of explorers who travel through a wormhole into another dimension, the 43-year-old hunk remained coy.

He teased: ''I mean, ['Interstellar' is] a much more story-driven picture [than 'The Dallas Buyers Club'].''

The inter-galactic adventured, written by Nolan and his brother Jonathan, boasts an all-star cast, led by McConaughey, Anne Hathaway and Jessica Chastain, as well as Matt Damon, Sir Michael Caine, Casey Affleck, John Lithgow and Topher Grace.

Although he refused to give any of 'The Dark Knight Rises' director's secrets away, Matthew did admit: ''[Nolan] knows what he wants. Oh yeah, he knows everything about what's happening on a film set, and what everybody's doing.''

'Insterstellar' - a co-production between Warner Bros. and Paramount Pictures - is thought to be based on physicist Kip S. Thorne's theory that wormholes exist and can be used for space travel.