Abigail Spencer has joined the cast of 'Oz, The Great and Powerful'.

The 'Mad Men' actress will star as an assistant to James Franco's titular character at the beginning of the movie, while he is still a magician in Kansas before he is whisked away to the magical world.

The 'Wizard Of Oz' prequel story - being directed by Sam Raimi - tells the tale of the man who lands himself in a place dominated by three sisters, witches played by 'Black Swan' star Mila Kunis, British actress Rachel Weisz and Oscar-nominated beauty Michelle Williams.

Oz helps Glinda - played by Michelle - battle for control of the kingdom.

Hilary Swank was once linked to one of the main witch roles, with Sam particularly keen to cast her, but no plans were announced.

Abigail has a number of movie projects coming up, including a part in Jon Favreau's 'Cowboys and Aliens' and a role in McG's 'This Means War' with Reese Witherspoon and Chris Pine.