Emily Mortimer is in negotiations to star opposite Ryan Reynolds in the romantic comedy "Chaos Theory" for Warner Independent Pictures and Castle Rock Entertainment.

Helmer Marcos Siega ("Pretty Persuasion") already has boarded the project, which is being produced by Frederic Golchan.

The story centers on a compulsive organizer (Reynolds) who decides to live his life without planning and in the process discovers love with Mortimer's character. Daniel Taplitz ("Breakin' All the Rules") penned the screenplay.

WIP's Mark Gill and Michael Andreen will oversee for the studio, while Martin Shafer and Liz Glotzer will shepherd for Castle Rock.

"Chaos" is set to start shooting in January in Vancouver.

"When I was thinking about this film, I had no idea what direction to go in. Then I saw 'Lovely & Amazing,' and I asked to take a meeting with (Mortimer), and luckily she liked the script," Siega said. "She adds depth to the movie, dimension, emotion. She elevates the film and makes the guys around her step up."

Golchan, who has been developing the project for more than a decade, said the studio was supportive of going with an up-and-coming actress and was very much behind Mortimer.

Her breakout performance in "Amazing" earned her critical praise and a 2003 Independent Spirit Award. The London native, daughter of famed writer John Mortimer, most recently starred in Shona Auerbach's "Dear Frankie." Her credits include "Young Adam," "Notting Hill" and "Elizabeth," as well as the upcoming films "The Pink Panther" and Woody Allen's "Match Point."

She is repped by WMA, Brillstein-Grey and attorney David Weber.