The two films center on a New York couple as they navigate through tough relationship problems; as indicated by the title, one film is from the perspective of McAvoy's character, and the other from Chastain's.
Isabelle Huppert, Viola Davis and William Hurt, among others, also star.
Here's the TIFF program notes:
The Disappearance of Eleanor Rigby: Him and Her is a two-part love story seen through the eyes of a New York couple trying to understand each other as they cope with personal hardship. The different perspectives of “Him” and “Her” result in two films with a unique look into one couple's attempt to reclaim the life and love they once had. Starring Jessica Chastain, James McAvoy, Nina Arianda, Viola Davis, Bill Hader, Ciarán Hinds, Isabelle Huppert, William Hurt, and Jess Weixler.