Romantic-comedy regular Dermot Mulroney to star in "Insidious : Chapter 3"
The Australian penned the first and second films in the series
Leigh Whannell and Angus Sampson will be back as Specs and Tucker
Will go head-to-head with the new Keanu Reeves film at the box-office
"Insidious : Chapter 2" debuted to more than $40 million at the box office making it one of the largest horror genre openings ever