http://www.darkhorizons.com/jessica-...filming-on-it/
So Jessica Chastain has filmed all of her scenes and has gone home, while everyone else is still filming.
Seems like the theory that they blew all their budget on her (and McAvoy) is probably true. You know, schedule all of the scenes involving the most expensive actress into the beginning most days (even if they're out of order) to get them done faster and out the door to reduce their going fee. Seems sound.