The script, which is being adapted by Ken Kwapis himself, is based on the novel of the same name by Diana Wagman. Here is a description of the story.
"Winnie Parker, mother to an angst-ridden teenage daughter and ex-wife of a famous game show host, is kidnapped. What follows is a psychological game of cat and mouse set in the kidnapper's tropically heated house-kept that way because the kidnapper is a reptile lover who has set up his home as a haven for Cookie, a menacing seven-foot long Iguana. While desperately seeking to escape, Winnie uncovers the mystery surrounding her captivity."
There is no set start date for the movie at this time. It is expected to be released sometime in late 2013.