Mackenzie Davis has joined the cast of Jason Reitman’s next feature, “Tully.”

Davis joins Charlize Theron in the film, which follows a mother of three (including a newborn), Marlo (Theron), who is gifted a night nanny by her brother. Hesitant to the extravagance at first, Marlo comes to form a unique bond with the thoughtful, surprising and sometimes challenging young nanny. […]