"We've been forging this friendship for over 25 years together… through this shared journey," the actress tells PEOPLE For Renée Zellweger, reuniting with Colin Firth and Hugh Grant on the set of Bridget Jones: Mad About the Boy was a bittersweet experience.

Mad about the Boy, Mark Darcy, the man of Bridget's dreams in the first three movies of the series, is tragically killed. But why?

Mad About the Boy" stars Renée Zellweger and Hugh Grant. Colin Firth also returns as Mark Darcy in a few scenes, with a catch.