The new movie is intended to be the eighth film in the 'DC Extended Universe' and a spin-off from "Suicide Squad" (2016).
Written by Christina Hodson, cast also includes Jurnee Smollett-Bell, Mary Elizabeth Winstead, Rosie Perez, Ella Jay Basco and Ewan McGregor.
"...since the events of 'Suicide Squad', 'Batman' has disappeared, leaving 'Gotham City' unprotected from crime, with 'Harley Quinn' breaking free of the slimy 'Joker'.
"Then when young 'Cassandra Cain', finds a diamond belonging to the criminal 'Black Mask', Harley recruits 'Black Canary', 'Huntress' and 'Renee Montoya' to help protect her..."
"I pitched the idea of an 'R-rated' girl gang film including 'Harley'," said Robbie, "because I was like, 'Harley needs friends' Harley loves interacting with people, so don't ever make her do a standalone film.