The Temp (1993)

A cookie company takeover has employees scrambling to make a case for continued employment. An executive's administrative assistant takes paternity leave, and he gets a temp who is too good to be true, doing tasks at a fast pace and doing quite a bit of creative work for the project. The executive starts noticing that all the obstacles to his climb up the corporate ladder are disappearing, including the death of some of his rivals. When his regular admin returns to work, his temp, who has made it clear that she wishes to stay with him, begins her own accelerated climb up the ladder, and he begins wondering if she was responsible for the removal of the obstacles.