The Sundance Film Festival selection will premiere on HBO at 8 PM (ET). Check local listings.

Academy Award winner Jim Broadbent and Samantha Morton star in the work that is "based on a true story of a respected politician who stakes his name and career to campaign for a notorious serial killer," according to the show materials. Andy Serkis and Lindsay Duncan also appear.

"Frank Aungier Pakenham, the 7th Earl of Longford, was one of the most controversial public figures in modern British history, an eccentric crusader with a proclivity for championing lost causes. But it was his last cause — an unlikely friendship with reviled child-killer Myra Hindley (a.k.a. 'the Moors Murderer') — that would undermine his political career and, possibly, her 36-year attempt to win her freedom."

Morgan's debut stage play Frost/Nixon will arrive on Broadway March 31 with original London stars Frank Langella and Michael Sheen. The scribe also penned the screenplays for "The Queen" and "The Last King of Scotland," which feature Academy Award-nominated performances by Helen Mirren and Forest Whitaker, respectively.

Tom Hooper directs "Longford" for HBO with executive producers Andy Harries and Morgan as well as producer Helen Flint. The film runs 92 minutes. For more information and a full schedule, visit hbo.com/films.