Doctor Who's current companion will star as an eccentric author suffering from writer's block after she finds success with a best-selling novel.
Black Death actor Emun Elliott will co-star as Gillan's publisher, who tries to make her life more miserable only to realise that he is in love with her.
Martin Compston (The Disappearance of Alice Creed) will also appear in Not Another Happy Ending, to be directed by John Mckay.
"We have two of the newest, hottest, sexiest pair of lead actors out of Scotland. Just right for the kind of quirky, romantic indie movie Not Another Happy Ending is set to be," Mckay told Screen Daily.
Filming is due to being at the end of 2011 or the beginning of 2012.
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Watch Karen Gillan in the new Doctor Who trailer below: