Andrea Riseborough is set to star opposite Alexander Skarsgard in Warner Bros.’ “The Hidden.”Matt and Ross Duffer will direct from their own spec script. Project is an elevated horror-thriller about a family hiding in a bomb shelter after escaping a mysterious outbreak. Roy Lee, Mason Novick, Lawrence Grey and Richard Zanuck will produce; John Middleton and Sebastian Aloi exec produce. WB acquired the Duffers’ spec late last year in a competitive situation. With Riseborough’s deal now done, the film should secure a greenlight shortly as one was contingent on getting its two stars to close deals. Riseborough is currently filming the sci-fi action pic “Oblivion” with Tom Cruise. She is repped by CAA, Independent Talent and Untitled.